Fixed #2443 -- Added DurationField.

A field for storing periods of time - modeled in Python by timedelta. It
is stored in the native interval data type on PostgreSQL and as a bigint
of microseconds on other backends.

Also includes significant changes to the internals of time related maths
in expressions, including the removal of DateModifierNode.

Thanks to Tim and Josh in particular for reviews.

django/db/backends/__init__.py

@@ -1,5 +1,6 @@
 from collections import deque
 import datetime
+import decimal
 import time
 import warnings
 
@@ -18,6 +19,7 @@ from django.db.backends.signals import connection_created
 from django.db.backends import utils
 from django.db.transaction import TransactionManagementError
 from django.db.utils import DatabaseError, DatabaseErrorWrapper, ProgrammingError
+from django.utils.dateparse import parse_duration
 from django.utils.deprecation import RemovedInDjango19Warning
 from django.utils.functional import cached_property
 from django.utils import six
@@ -575,6 +577,9 @@ class BaseDatabaseFeatures(object):
 
     supports_binary_field = True
 
+    # Is there a true datatype for timedeltas?
+    has_native_duration_field = False
+
     # Do time/datetime fields have microsecond precision?
     supports_microsecond_precision = True
 
@@ -1251,8 +1256,16 @@ class BaseDatabaseOperations(object):
         Some field types on some backends do not provide data in the correct
         format, this is the hook for coverter functions.
         """
+        if not self.connection.features.has_native_duration_field and internal_type == 'DurationField':
+            return [self.convert_durationfield_value]
         return []
 
+    def convert_durationfield_value(self, value, field):
+        if value is not None:
+            value = str(decimal.Decimal(value) / decimal.Decimal(1000000))
+            value = parse_duration(value)
+        return value
+
     def check_aggregate_support(self, aggregate_func):
         """Check that the backend supports the provided aggregate
 
@@ -1272,6 +1285,9 @@ class BaseDatabaseOperations(object):
         conn = ' %s ' % connector
         return conn.join(sub_expressions)
 
+    def combine_duration_expression(self, connector, sub_expressions):
+        return self.combine_expression(connector, sub_expressions)
+
     def modify_insert_params(self, placeholders, params):
         """Allow modification of insert parameters. Needed for Oracle Spatial
         backend due to #10888.

django/db/backends/mysql/base.py

@@ -289,9 +289,12 @@ class DatabaseOperations(BaseDatabaseOperations):
             sql = "CAST(DATE_FORMAT(%s, '%s') AS DATETIME)" % (field_name, format_str)
         return sql, params
 
-    def date_interval_sql(self, sql, connector, timedelta):
-        return "(%s %s INTERVAL '%d 0:0:%d:%d' DAY_MICROSECOND)" % (sql, connector,
-                timedelta.days, timedelta.seconds, timedelta.microseconds)
+    def date_interval_sql(self, timedelta):
+        return "INTERVAL '%d 0:0:%d:%d' DAY_MICROSECOND" % (
+            timedelta.days, timedelta.seconds, timedelta.microseconds), []
+
+    def format_for_duration_arithmetic(self, sql):
+        return 'INTERVAL %s MICROSECOND' % sql
 
     def drop_foreignkey_sql(self):
         return "DROP FOREIGN KEY"

django/db/backends/mysql/creation.py

@@ -16,6 +16,7 @@ class DatabaseCreation(BaseDatabaseCreation):
         'DateField': 'date',
         'DateTimeField': 'datetime',
         'DecimalField': 'numeric(%(max_digits)s, %(decimal_places)s)',
+        'DurationField': 'bigint',
         'FileField': 'varchar(%(max_length)s)',
         'FilePathField': 'varchar(%(max_length)s)',
         'FloatField': 'double precision',

django/db/backends/oracle/base.py

@@ -198,19 +198,22 @@ WHEN (new.%(col_name)s IS NULL)
             # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions050.htm
             return "EXTRACT(%s FROM %s)" % (lookup_type.upper(), field_name)
 
-    def date_interval_sql(self, sql, connector, timedelta):
+    def date_interval_sql(self, timedelta):
         """
         Implements the interval functionality for expressions
         format for Oracle:
-        (datefield + INTERVAL '3 00:03:20.000000' DAY(1) TO SECOND(6))
+        INTERVAL '3 00:03:20.000000' DAY(1) TO SECOND(6)
         """
         minutes, seconds = divmod(timedelta.seconds, 60)
         hours, minutes = divmod(minutes, 60)
         days = str(timedelta.days)
         day_precision = len(days)
-        fmt = "(%s %s INTERVAL '%s %02d:%02d:%02d.%06d' DAY(%d) TO SECOND(6))"
-        return fmt % (sql, connector, days, hours, minutes, seconds,
-                timedelta.microseconds, day_precision)
+        fmt = "INTERVAL '%s %02d:%02d:%02d.%06d' DAY(%d) TO SECOND(6)"
+        return fmt % (days, hours, minutes, seconds, timedelta.microseconds,
+                day_precision), []
+
+    def format_for_duration_arithmetic(self, sql):
+        return "NUMTODSINTERVAL(%s / 100000, 'SECOND')" % sql
 
     def date_trunc_sql(self, lookup_type, field_name):
         # http://docs.oracle.com/cd/B19306_01/server.102/b14200/functions230.htm#i1002084

django/db/backends/oracle/creation.py

@@ -29,6 +29,7 @@ class DatabaseCreation(BaseDatabaseCreation):
         'DateField': 'DATE',
         'DateTimeField': 'TIMESTAMP',
         'DecimalField': 'NUMBER(%(max_digits)s, %(decimal_places)s)',
+        'DurationField': 'NUMBER(19)',
         'FileField': 'NVARCHAR2(%(max_length)s)',
         'FilePathField': 'NVARCHAR2(%(max_length)s)',
         'FloatField': 'DOUBLE PRECISION',

django/db/backends/postgresql_psycopg2/base.py

@@ -47,6 +47,7 @@ class DatabaseFeatures(BaseDatabaseFeatures):
     needs_datetime_string_cast = False
     can_return_id_from_insert = True
     has_real_datatype = True
+    has_native_duration_field = True
     can_defer_constraint_checks = True
     has_select_for_update = True
     has_select_for_update_nowait = True

django/db/backends/postgresql_psycopg2/creation.py

@@ -16,6 +16,7 @@ class DatabaseCreation(BaseDatabaseCreation):
         'DateField': 'date',
         'DateTimeField': 'timestamp with time zone',
         'DecimalField': 'numeric(%(max_digits)s, %(decimal_places)s)',
+        'DurationField': 'interval',
         'FileField': 'varchar(%(max_length)s)',
         'FilePathField': 'varchar(%(max_length)s)',
         'FloatField': 'double precision',

django/db/backends/postgresql_psycopg2/operations.py

@@ -16,23 +16,6 @@ class DatabaseOperations(BaseDatabaseOperations):
         else:
             return "EXTRACT('%s' FROM %s)" % (lookup_type, field_name)
 
-    def date_interval_sql(self, sql, connector, timedelta):
-        """
-        implements the interval functionality for expressions
-        format for Postgres:
-            (datefield + interval '3 days 200 seconds 5 microseconds')
-        """
-        modifiers = []
-        if timedelta.days:
-            modifiers.append('%s days' % timedelta.days)
-        if timedelta.seconds:
-            modifiers.append('%s seconds' % timedelta.seconds)
-        if timedelta.microseconds:
-            modifiers.append('%s microseconds' % timedelta.microseconds)
-        mods = ' '.join(modifiers)
-        conn = ' %s ' % connector
-        return '(%s)' % conn.join([sql, 'interval \'%s\'' % mods])
-
     def date_trunc_sql(self, lookup_type, field_name):
         # http://www.postgresql.org/docs/current/static/functions-datetime.html#FUNCTIONS-DATETIME-TRUNC
         return "DATE_TRUNC('%s', %s)" % (lookup_type, field_name)

django/db/backends/sqlite3/base.py

@@ -21,7 +21,8 @@ from django.db.backends.sqlite3.creation import DatabaseCreation
 from django.db.backends.sqlite3.introspection import DatabaseIntrospection
 from django.db.backends.sqlite3.schema import DatabaseSchemaEditor
 from django.db.models import fields, aggregates
-from django.utils.dateparse import parse_date, parse_datetime, parse_time
+from django.utils.dateparse import parse_date, parse_datetime, parse_time, parse_duration
+from django.utils.duration import duration_string
 from django.utils.encoding import force_text
 from django.utils.functional import cached_property
 from django.utils.safestring import SafeBytes
@@ -175,15 +176,12 @@ class DatabaseOperations(BaseDatabaseOperations):
         # cause a collision with a field name).
         return "django_date_extract('%s', %s)" % (lookup_type.lower(), field_name)
 
-    def date_interval_sql(self, sql, connector, timedelta):
-        # It would be more straightforward if we could use the sqlite strftime
-        # function, but it does not allow for keeping six digits of fractional
-        # second information, nor does it allow for formatting date and datetime
-        # values differently. So instead we register our own function that
-        # formats the datetime combined with the delta in a manner suitable
-        # for comparisons.
-        return 'django_format_dtdelta(%s, "%s", "%d", "%d", "%d")' % (sql,
-            connector, timedelta.days, timedelta.seconds, timedelta.microseconds)
+    def date_interval_sql(self, timedelta):
+        return "'%s'" % duration_string(timedelta), []
+
+    def format_for_duration_arithmetic(self, sql):
+        """Do nothing here, we will handle it in the custom function."""
+        return sql
 
     def date_trunc_sql(self, lookup_type, field_name):
         # sqlite doesn't support DATE_TRUNC, so we fake it with a user-defined
@@ -314,6 +312,14 @@ class DatabaseOperations(BaseDatabaseOperations):
             return 'django_power(%s)' % ','.join(sub_expressions)
         return super(DatabaseOperations, self).combine_expression(connector, sub_expressions)
 
+    def combine_duration_expression(self, connector, sub_expressions):
+        if connector not in ['+', '-']:
+            raise utils.DatabaseError('Invalid connector for timedelta: %s.' % connector)
+        fn_params = ["'%s'" % connector] + sub_expressions
+        if len(fn_params) > 3:
+            raise ValueError('Too many params for timedelta operations.')
+        return "django_format_dtdelta(%s)" % ', '.join(fn_params)
+
     def integer_field_range(self, internal_type):
         # SQLite doesn't enforce any integer constraints
         return (None, None)
@@ -408,7 +414,7 @@ class DatabaseWrapper(BaseDatabaseWrapper):
         conn.create_function("django_datetime_extract", 3, _sqlite_datetime_extract)
         conn.create_function("django_datetime_trunc", 3, _sqlite_datetime_trunc)
         conn.create_function("regexp", 2, _sqlite_regexp)
-        conn.create_function("django_format_dtdelta", 5, _sqlite_format_dtdelta)
+        conn.create_function("django_format_dtdelta", 3, _sqlite_format_dtdelta)
         conn.create_function("django_power", 2, _sqlite_power)
         return conn
 
@@ -585,19 +591,33 @@ def _sqlite_datetime_trunc(lookup_type, dt, tzname):
         return "%i-%02i-%02i %02i:%02i:%02i" % (dt.year, dt.month, dt.day, dt.hour, dt.minute, dt.second)
 
 
-def _sqlite_format_dtdelta(dt, conn, days, secs, usecs):
+def _sqlite_format_dtdelta(conn, lhs, rhs):
+    """
+    LHS and RHS can be either:
+        - An integer number of microseconds
+        - A string representing a timedelta object
+        - A string representing a datetime
+    """
     try:
-        dt = backend_utils.typecast_timestamp(dt)
-        delta = datetime.timedelta(int(days), int(secs), int(usecs))
+        if isinstance(lhs, int):
+            lhs = str(decimal.Decimal(lhs) / decimal.Decimal(1000000))
+        real_lhs = parse_duration(lhs)
+        if real_lhs is None:
+            real_lhs = backend_utils.typecast_timestamp(lhs)
+        if isinstance(rhs, int):
+            rhs = str(decimal.Decimal(rhs) / decimal.Decimal(1000000))
+        real_rhs = parse_duration(rhs)
+        if real_rhs is None:
+            real_rhs = backend_utils.typecast_timestamp(rhs)
         if conn.strip() == '+':
-            dt = dt + delta
+            out = real_lhs + real_rhs
         else:
-            dt = dt - delta
+            out = real_lhs - real_rhs
     except (ValueError, TypeError):
         return None
     # typecast_timestamp returns a date or a datetime without timezone.
     # It will be formatted as "%Y-%m-%d" or "%Y-%m-%d %H:%M:%S[.%f]"
-    return str(dt)
+    return str(out)
 
 
 def _sqlite_regexp(re_pattern, re_string):

django/db/backends/sqlite3/creation.py

@@ -18,6 +18,7 @@ class DatabaseCreation(BaseDatabaseCreation):
         'DateField': 'date',
         'DateTimeField': 'datetime',
         'DecimalField': 'decimal',
+        'DurationField': 'bigint',
         'FileField': 'varchar(%(max_length)s)',
         'FilePathField': 'varchar(%(max_length)s)',
         'FloatField': 'real',

django/db/models/expressions.py

@@ -34,12 +34,12 @@ class CombinableMixin(object):
     BITOR = '|'
 
     def _combine(self, other, connector, reversed, node=None):
-        if isinstance(other, datetime.timedelta):
-            return DateModifierNode(self, connector, other)
-
         if not hasattr(other, 'resolve_expression'):
             # everything must be resolvable to an expression
-            other = Value(other)
+            if isinstance(other, datetime.timedelta):
+                other = DurationValue(other, output_field=fields.DurationField())
+            else:
+                other = Value(other)
 
         if reversed:
             return Expression(other, connector, self)
@@ -333,6 +333,18 @@ class Expression(ExpressionNode):
         self.lhs, self.rhs = exprs
 
     def as_sql(self, compiler, connection):
+        try:
+            lhs_output = self.lhs.output_field
+        except FieldError:
+            lhs_output = None
+        try:
+            rhs_output = self.rhs.output_field
+        except FieldError:
+            rhs_output = None
+        if (not connection.features.has_native_duration_field and
+                ((lhs_output and lhs_output.get_internal_type() == 'DurationField')
+                or (rhs_output and rhs_output.get_internal_type() == 'DurationField'))):
+            return DurationExpression(self.lhs, self.connector, self.rhs).as_sql(compiler, connection)
         expressions = []
         expression_params = []
         sql, params = compiler.compile(self.lhs)
@@ -354,45 +366,31 @@ class Expression(ExpressionNode):
         return c
 
 
-class DateModifierNode(Expression):
-    """
-    Node that implements the following syntax:
-    filter(end_date__gt=F('start_date') + datetime.timedelta(days=3, seconds=200))
-
-    which translates into:
-    POSTGRES:
-        WHERE end_date > (start_date + INTERVAL '3 days 200 seconds')
-
-    MYSQL:
-        WHERE end_date > (start_date + INTERVAL '3 0:0:200:0' DAY_MICROSECOND)
-
-    ORACLE:
-        WHERE end_date > (start_date + INTERVAL '3 00:03:20.000000' DAY(1) TO SECOND(6))
-
-    SQLITE:
-        WHERE end_date > django_format_dtdelta(start_date, "+" "3", "200", "0")
-        (A custom function is used in order to preserve six digits of fractional
-        second information on sqlite, and to format both date and datetime values.)
-
-    Note that microsecond comparisons are not well supported with MySQL, since
-    MySQL does not store microsecond information.
-
-    Only adding and subtracting timedeltas is supported, attempts to use other
-    operations raise a TypeError.
-    """
-    def __init__(self, lhs, connector, rhs):
-        if not isinstance(rhs, datetime.timedelta):
-            raise TypeError('rhs must be a timedelta.')
-        if connector not in (self.ADD, self.SUB):
-            raise TypeError('Connector must be + or -, not %s' % connector)
-        super(DateModifierNode, self).__init__(lhs, connector, Value(rhs))
+class DurationExpression(Expression):
+    def compile(self, side, compiler, connection):
+        if not isinstance(side, DurationValue):
+            try:
+                output = side.output_field
+            except FieldError:
+                pass
+            if output.get_internal_type() == 'DurationField':
+                sql, params = compiler.compile(side)
+                return connection.ops.format_for_duration_arithmetic(sql), params
+        return compiler.compile(side)
 
     def as_sql(self, compiler, connection):
-        timedelta = self.rhs.value
-        sql, params = compiler.compile(self.lhs)
-        if (timedelta.days == timedelta.seconds == timedelta.microseconds == 0):
-            return sql, params
-        return connection.ops.date_interval_sql(sql, self.connector, timedelta), params
+        expressions = []
+        expression_params = []
+        sql, params = self.compile(self.lhs, compiler, connection)
+        expressions.append(sql)
+        expression_params.extend(params)
+        sql, params = self.compile(self.rhs, compiler, connection)
+        expressions.append(sql)
+        expression_params.extend(params)
+        # order of precedence
+        expression_wrapper = '(%s)'
+        sql = connection.ops.combine_duration_expression(self.connector, expressions)
+        return expression_wrapper % sql, expression_params
 
 
 class F(CombinableMixin):
@@ -488,6 +486,13 @@ class Value(ExpressionNode):
         return '%s', [self.value]
 
 
+class DurationValue(Value):
+    def as_sql(self, compiler, connection):
+        if connection.features.has_native_duration_field:
+            return super(DurationValue, self).as_sql(compiler, connection)
+        return connection.ops.date_interval_sql(self.value)
+
+
 class Col(ExpressionNode):
     def __init__(self, alias, target, source=None):
         if source is None:

django/db/models/fields/__init__.py

@@ -19,8 +19,9 @@ from django.conf import settings
 from django import forms
 from django.core import exceptions, validators, checks
 from django.utils.datastructures import DictWrapper
-from django.utils.dateparse import parse_date, parse_datetime, parse_time
+from django.utils.dateparse import parse_date, parse_datetime, parse_time, parse_duration
 from django.utils.deprecation import RemovedInDjango19Warning
+from django.utils.duration import duration_string
 from django.utils.functional import cached_property, curry, total_ordering, Promise
 from django.utils.text import capfirst
 from django.utils import timezone
@@ -36,8 +37,8 @@ from django.utils.itercompat import is_iterable
 __all__ = [str(x) for x in (
     'AutoField', 'BLANK_CHOICE_DASH', 'BigIntegerField', 'BinaryField',
     'BooleanField', 'CharField', 'CommaSeparatedIntegerField', 'DateField',
-    'DateTimeField', 'DecimalField', 'EmailField', 'Empty', 'Field',
-    'FieldDoesNotExist', 'FilePathField', 'FloatField',
+    'DateTimeField', 'DecimalField', 'DurationField', 'EmailField', 'Empty',
+    'Field', 'FieldDoesNotExist', 'FilePathField', 'FloatField',
     'GenericIPAddressField', 'IPAddressField', 'IntegerField', 'NOT_PROVIDED',
     'NullBooleanField', 'PositiveIntegerField', 'PositiveSmallIntegerField',
     'SlugField', 'SmallIntegerField', 'TextField', 'TimeField', 'URLField',
@@ -1573,6 +1574,50 @@ class DecimalField(Field):
         return super(DecimalField, self).formfield(**defaults)
 
 
+class DurationField(Field):
+    """Stores timedelta objects.
+
+    Uses interval on postgres, bigint of microseconds on other databases.
+    """
+    empty_strings_allowed = False
+    default_error_messages = {
+        'invalid': _("'%(value)s' value has an invalid format. It must be in "
+                     "[DD] [HH:[MM:]]ss[.uuuuuu] format.")
+    }
+    description = _("Duration")
+
+    def get_internal_type(self):
+        return "DurationField"
+
+    def to_python(self, value):
+        if value is None:
+            return value
+        if isinstance(value, datetime.timedelta):
+            return value
+        try:
+            parsed = parse_duration(value)
+        except ValueError:
+            pass
+        else:
+            if parsed is not None:
+                return parsed
+
+        raise exceptions.ValidationError(
+            self.error_messages['invalid'],
+            code='invalid',
+            params={'value': value},
+        )
+
+    def get_db_prep_value(self, value, connection, prepared=False):
+        if connection.features.has_native_duration_field:
+            return value
+        return value.total_seconds() * 1000000
+
+    def value_to_string(self, obj):
+        val = self._get_val_from_obj(obj)
+        return '' if val is None else duration_string(val)
+
+
 class EmailField(CharField):
     default_validators = [validators.validate_email]
     description = _("Email address")

django/forms/fields.py

@@ -26,7 +26,9 @@ from django.forms.widgets import (
 from django.utils import formats
 from django.utils.encoding import smart_text, force_str, force_text
 from django.utils.ipv6 import clean_ipv6_address
+from django.utils.dateparse import parse_duration
 from django.utils.deprecation import RemovedInDjango19Warning, RemovedInDjango20Warning, RenameMethodsBase
+from django.utils.duration import duration_string
 from django.utils import six
 from django.utils.six.moves.urllib.parse import urlsplit, urlunsplit
 from django.utils.translation import ugettext_lazy as _, ungettext_lazy
@@ -37,7 +39,7 @@ from django.core.validators import EMPTY_VALUES  # NOQA
 
 __all__ = (
     'Field', 'CharField', 'IntegerField',
-    'DateField', 'TimeField', 'DateTimeField',
+    'DateField', 'TimeField', 'DateTimeField', 'DurationField',
     'RegexField', 'EmailField', 'FileField', 'ImageField', 'URLField',
     'BooleanField', 'NullBooleanField', 'ChoiceField', 'MultipleChoiceField',
     'ComboField', 'MultiValueField', 'FloatField', 'DecimalField',
@@ -518,6 +520,25 @@ class DateTimeField(BaseTemporalField):
         return datetime.datetime.strptime(force_str(value), format)
 
 
+class DurationField(Field):
+    default_error_messages = {
+        'invalid': _('Enter a valid duration.'),
+    }
+
+    def prepare_value(self, value):
+        return duration_string(value)
+
+    def to_python(self, value):
+        if value in self.empty_values:
+            return None
+        if isinstance(value, datetime.timedelta):
+            return value
+        value = parse_duration(value)
+        if value is None:
+            raise ValidationError(self.error_messages['invalid'], code='invalid')
+        return value
+
+
 class RegexField(CharField):
     def __init__(self, regex, max_length=None, min_length=None, error_message=None, *args, **kwargs):
         """

django/utils/dateparse.py

@@ -27,6 +27,29 @@ datetime_re = re.compile(
     r'(?P<tzinfo>Z|[+-]\d{2}(?::?\d{2})?)?$'
 )
 
+standard_duration_re = re.compile(
+    r'^'
+    r'(?:(?P<days>-?\d+) )?'
+    r'((?:(?P<hours>\d+):)(?=\d+:\d+))?'
+    r'(?:(?P<minutes>\d+):)?'
+    r'(?P<seconds>\d+)'
+    r'(?:\.(?P<microseconds>\d{1,6})\d{0,6})?'
+    r'$'
+)
+
+# Support the sections of ISO 8601 date representation that are accepted by
+# timedelta
+iso8601_duration_re = re.compile(
+    r'^P'
+    r'(?:(?P<days>\d+(.\d+)?)D)?'
+    r'(?:T'
+    r'(?:(?P<hours>\d+(.\d+)?)H)?'
+    r'(?:(?P<minutes>\d+(.\d+)?)M)?'
+    r'(?:(?P<seconds>\d+(.\d+)?)S)?'
+    r')?'
+    r'$'
+)
+
 
 def parse_date(value):
     """Parses a string and return a datetime.date.
@@ -84,3 +107,21 @@ def parse_datetime(value):
         kw = {k: int(v) for k, v in six.iteritems(kw) if v is not None}
         kw['tzinfo'] = tzinfo
         return datetime.datetime(**kw)
+
+
+def parse_duration(value):
+    """Parses a duration string and returns a datetime.timedelta.
+
+    The preferred format for durations in Django is '%d %H:%M:%S.%f'.
+
+    Also supports ISO 8601 representation.
+    """
+    match = standard_duration_re.match(value)
+    if not match:
+        match = iso8601_duration_re.match(value)
+    if match:
+        kw = match.groupdict()
+        if kw.get('microseconds'):
+            kw['microseconds'] = kw['microseconds'].ljust(6, '0')
+        kw = {k: float(v) for k, v in six.iteritems(kw) if v is not None}
+        return datetime.timedelta(**kw)

django/utils/duration.py

@@ -0,0 +1,21 @@
+"""Version of str(timedelta) which is not English specific."""
+
+
+def duration_string(duration):
+    days = duration.days
+    seconds = duration.seconds
+    microseconds = duration.microseconds
+
+    minutes = seconds // 60
+    seconds = seconds % 60
+
+    hours = minutes // 60
+    minutes = minutes % 60
+
+    string = '{:02d}:{:02d}:{:02d}'.format(hours, minutes, seconds)
+    if days:
+        string = '{} '.format(days) + string
+    if microseconds:
+        string += '.{:06d}'.format(microseconds)
+
+    return string

docs/ref/forms/fields.txt

@@ -546,6 +546,23 @@ For each field, we describe the default widget used if you don't specify
 
         The maximum number of decimal places permitted.
 
+``DurationField``
+~~~~~~~~~~~~~~~~~
+
+.. versionadded:: 1.8
+
+.. class:: DurationField(**kwargs)
+
+    * Default widget: :class:`TextInput`
+    * Empty value: ``None``
+    * Normalizes to: A Python :class:`~python:datetime.timedelta`.
+    * Validates that the given value is a string which can be converted into a
+      ``timedelta``.
+    * Error message keys: ``required``, ``invalid``.
+
+    Accepts any format understood by
+    :func:`~django.utils.dateparse.parse_duration`.
+
 ``EmailField``
 ~~~~~~~~~~~~~~
 

docs/ref/models/fields.txt

@@ -542,6 +542,23 @@ The default form widget for this field is a :class:`~django.forms.TextInput`.
     :class:`FloatField` and :class:`DecimalField` classes, please
     see :ref:`FloatField vs. DecimalField <floatfield_vs_decimalfield>`.
 
+``DurationField``
+-----------------
+
+.. versionadded:: 1.8
+
+.. class:: DurationField([**options])
+
+A field for storing periods of time - modeled in Python by
+:class:`~python:datetime.timedelta`. When used on PostgreSQL, the data type
+used is an ``interval``, otherwise a ``bigint`` of microseconds is used.
+
+.. note::
+
+    Arithmetic with ``DurationField`` works in most cases. However on all
+    databases other than PostgreSQL, comparing the value of a ``DurationField``
+    to arithmetic on ``DateTimeField`` instances will not work as expected.
+
 ``EmailField``
 --------------
 

docs/ref/utils.txt

@@ -158,6 +158,15 @@ The functions defined in this module share the following properties:
     ``tzinfo`` attribute is a :class:`~django.utils.tzinfo.FixedOffset`
     instance.
 
+.. function:: parse_duration(value)
+
+    .. versionadded:: 1.8
+
+    Parses a string and returns a :class:`datetime.timedelta`.
+
+    Expects data in the format ``"DD HH:MM:SS.uuuuuu"`` or as specified by ISO
+    8601 (e.g. ``P4DT1H15M20S`` which is equivalent to ``4 1:15:20``).
+
 ``django.utils.decorators``
 ===========================
 

docs/releases/1.8.txt

@@ -54,9 +54,16 @@ New data types
 ~~~~~~~~~~~~~~
 
 * Django now has a :class:`~django.db.models.UUIDField` for storing
-  universally unique identifiers. There is a corresponding :class:`form field
-  <django.forms.UUIDField>`. It is stored as the native ``uuid`` data type on
-  PostgreSQL and as a fixed length character field on other backends.
+  universally unique identifiers. It is stored as the native ``uuid`` data type
+  on PostgreSQL and as a fixed length character field on other backends. There
+  is a corresponding :class:`form field <django.forms.UUIDField>`.
+
+* Django now has a :class:`~django.db.models.DurationField` for storing periods
+  of time - modeled in Python by :class:`~python:datetime.timedelta`. It is
+  stored in the native ``interval`` data type on PostgreSQL and as a ``bigint``
+  of microseconds on other backends. Date and time related arithmetic has also
+  been improved on all backends. There is a corresponding :class:`form field
+  <django.forms.DurationField>`.
 
 Query Expressions
 ~~~~~~~~~~~~~~~~~

tests/expressions/models.py

@@ -47,6 +47,7 @@ class Experiment(models.Model):
     name = models.CharField(max_length=24)
     assigned = models.DateField()
     completed = models.DateField()
+    estimated_time = models.DurationField()
     start = models.DateTimeField()
     end = models.DateTimeField()
 

tests/expressions/tests.py

@@ -4,7 +4,7 @@ from copy import deepcopy
 import datetime
 
 from django.core.exceptions import FieldError
-from django.db import connection, transaction
+from django.db import connection, transaction, DatabaseError
 from django.db.models import F
 from django.test import TestCase, skipIfDBFeature, skipUnlessDBFeature
 from django.test.utils import Approximate
@@ -602,7 +602,7 @@ class FTimeDeltaTests(TestCase):
         # e0: started same day as assigned, zero duration
         end = stime + delta0
         e0 = Experiment.objects.create(name='e0', assigned=sday, start=stime,
-            end=end, completed=end.date())
+            end=end, completed=end.date(), estimated_time=delta0)
         self.deltas.append(delta0)
         self.delays.append(e0.start -
             datetime.datetime.combine(e0.assigned, midnight))
@@ -617,7 +617,7 @@ class FTimeDeltaTests(TestCase):
             delay = datetime.timedelta(1)
             end = stime + delay + delta1
             e1 = Experiment.objects.create(name='e1', assigned=sday,
-                start=stime + delay, end=end, completed=end.date())
+                start=stime + delay, end=end, completed=end.date(), estimated_time=delta1)
             self.deltas.append(delta1)
             self.delays.append(e1.start -
                 datetime.datetime.combine(e1.assigned, midnight))
@@ -627,7 +627,7 @@ class FTimeDeltaTests(TestCase):
         end = stime + delta2
         e2 = Experiment.objects.create(name='e2',
             assigned=sday - datetime.timedelta(3), start=stime, end=end,
-            completed=end.date())
+            completed=end.date(), estimated_time=datetime.timedelta(hours=1))
         self.deltas.append(delta2)
         self.delays.append(e2.start -
             datetime.datetime.combine(e2.assigned, midnight))
@@ -637,7 +637,7 @@ class FTimeDeltaTests(TestCase):
         delay = datetime.timedelta(4)
         end = stime + delay + delta3
         e3 = Experiment.objects.create(name='e3',
-            assigned=sday, start=stime + delay, end=end, completed=end.date())
+            assigned=sday, start=stime + delay, end=end, completed=end.date(), estimated_time=delta3)
         self.deltas.append(delta3)
         self.delays.append(e3.start -
             datetime.datetime.combine(e3.assigned, midnight))
@@ -647,7 +647,7 @@ class FTimeDeltaTests(TestCase):
         end = stime + delta4
         e4 = Experiment.objects.create(name='e4',
             assigned=sday - datetime.timedelta(10), start=stime, end=end,
-            completed=end.date())
+            completed=end.date(), estimated_time=delta4 - datetime.timedelta(1))
         self.deltas.append(delta4)
         self.delays.append(e4.start -
             datetime.datetime.combine(e4.assigned, midnight))
@@ -675,6 +675,10 @@ class FTimeDeltaTests(TestCase):
                 Experiment.objects.filter(end__lt=F('start') + delta)]
             self.assertEqual(test_set, self.expnames[:i])
 
+            test_set = [e.name for e in
+                Experiment.objects.filter(end__lt=delta + F('start'))]
+            self.assertEqual(test_set, self.expnames[:i])
+
             test_set = [e.name for e in
                 Experiment.objects.filter(end__lte=F('start') + delta)]
             self.assertEqual(test_set, self.expnames[:i + 1])
@@ -756,42 +760,29 @@ class FTimeDeltaTests(TestCase):
             self.assertEqual(expected_ends, new_ends)
             self.assertEqual(expected_durations, new_durations)
 
-    def test_delta_invalid_op_mult(self):
-        raised = False
-        try:
-            repr(Experiment.objects.filter(end__lt=F('start') * self.deltas[0]))
-        except TypeError:
-            raised = True
-        self.assertTrue(raised, "TypeError not raised on attempt to multiply datetime by timedelta.")
-
-    def test_delta_invalid_op_div(self):
-        raised = False
-        try:
-            repr(Experiment.objects.filter(end__lt=F('start') / self.deltas[0]))
-        except TypeError:
-            raised = True
-        self.assertTrue(raised, "TypeError not raised on attempt to divide datetime by timedelta.")
-
-    def test_delta_invalid_op_mod(self):
-        raised = False
-        try:
-            repr(Experiment.objects.filter(end__lt=F('start') % self.deltas[0]))
-        except TypeError:
-            raised = True
-        self.assertTrue(raised, "TypeError not raised on attempt to modulo divide datetime by timedelta.")
-
-    def test_delta_invalid_op_and(self):
-        raised = False
-        try:
-            repr(Experiment.objects.filter(end__lt=F('start').bitand(self.deltas[0])))
-        except TypeError:
-            raised = True
-        self.assertTrue(raised, "TypeError not raised on attempt to binary and a datetime with a timedelta.")
-
-    def test_delta_invalid_op_or(self):
-        raised = False
-        try:
-            repr(Experiment.objects.filter(end__lt=F('start').bitor(self.deltas[0])))
-        except TypeError:
-            raised = True
-        self.assertTrue(raised, "TypeError not raised on attempt to binary or a datetime with a timedelta.")
+    def test_invalid_operator(self):
+        with self.assertRaises(DatabaseError):
+            list(Experiment.objects.filter(start=F('start') * datetime.timedelta(0)))
+
+    def test_durationfield_add(self):
+        zeros = [e.name for e in
+            Experiment.objects.filter(start=F('start') + F('estimated_time'))]
+        self.assertEqual(zeros, ['e0'])
+
+        end_less = [e.name for e in
+            Experiment.objects.filter(end__lt=F('start') + F('estimated_time'))]
+        self.assertEqual(end_less, ['e2'])
+
+        delta_math = [e.name for e in
+            Experiment.objects.filter(end__gte=F('start') + F('estimated_time') + datetime.timedelta(hours=1))]
+        self.assertEqual(delta_math, ['e4'])
+
+    @skipUnlessDBFeature("has_native_duration_field")
+    def test_date_subtraction(self):
+        under_estimate = [e.name for e in
+            Experiment.objects.filter(estimated_time__gt=F('end') - F('start'))]
+        self.assertEqual(under_estimate, ['e2'])
+
+        over_estimate = [e.name for e in
+            Experiment.objects.filter(estimated_time__lt=F('end') - F('start'))]
+        self.assertEqual(over_estimate, ['e4'])

tests/forms_tests/tests/test_fields.py

@@ -43,11 +43,12 @@ except ImportError:
 from django.core.files.uploadedfile import SimpleUploadedFile
 from django.forms import (
     BooleanField, CharField, ChoiceField, ComboField, DateField, DateTimeField,
-    DecimalField, EmailField, Field, FileField, FilePathField, FloatField,
-    Form, forms, HiddenInput, ImageField, IntegerField, MultipleChoiceField,
-    NullBooleanField, NumberInput, PasswordInput, RadioSelect, RegexField,
-    SplitDateTimeField, TextInput, Textarea, TimeField, TypedChoiceField,
-    TypedMultipleChoiceField, URLField, UUIDField, ValidationError, Widget,
+    DecimalField, DurationField, EmailField, Field, FileField, FilePathField,
+    FloatField, Form, forms, HiddenInput, ImageField, IntegerField,
+    MultipleChoiceField, NullBooleanField, NumberInput, PasswordInput,
+    RadioSelect, RegexField, SplitDateTimeField, TextInput, Textarea,
+    TimeField, TypedChoiceField, TypedMultipleChoiceField, URLField, UUIDField,
+    ValidationError, Widget,
 )
 from django.test import SimpleTestCase
 from django.utils import formats
@@ -611,6 +612,32 @@ class FieldsTests(SimpleTestCase):
 
     # RegexField ##################################################################
 
+    def test_durationfield_1(self):
+        f = DurationField()
+        self.assertEqual(datetime.timedelta(seconds=30), f.clean('30'))
+        self.assertEqual(
+            datetime.timedelta(minutes=15, seconds=30),
+            f.clean('15:30')
+        )
+        self.assertEqual(
+            datetime.timedelta(hours=1, minutes=15, seconds=30),
+            f.clean('1:15:30')
+        )
+        self.assertEqual(
+            datetime.timedelta(
+                days=1, hours=1, minutes=15, seconds=30, milliseconds=300),
+            f.clean('1 1:15:30.3')
+        )
+
+    def test_durationfield_2(self):
+        class DurationForm(Form):
+            duration = DurationField(initial=datetime.timedelta(hours=1))
+        f = DurationForm()
+        self.assertHTMLEqual(
+            '<input id="id_duration" type="text" name="duration" value="01:00:00">',
+            str(f['duration'])
+        )
+
     def test_regexfield_1(self):
         f = RegexField('^[0-9][A-F][0-9]$')
         self.assertEqual('2A2', f.clean('2A2'))

tests/model_fields/models.py

@@ -121,6 +121,10 @@ class DateTimeModel(models.Model):
     t = models.TimeField()
 
 
+class DurationModel(models.Model):
+    field = models.DurationField()
+
+
 class PrimaryKeyCharModel(models.Model):
     string = models.CharField(max_length=10, primary_key=True)
 

tests/model_fields/test_durationfield.py

@@ -0,0 +1,67 @@
+import datetime
+import json
+
+from django.core import exceptions, serializers
+from django.db import models
+from django.test import TestCase
+
+from .models import DurationModel
+
+
+class TestSaveLoad(TestCase):
+
+    def test_simple_roundtrip(self):
+        duration = datetime.timedelta(days=123, seconds=123, microseconds=123)
+        DurationModel.objects.create(field=duration)
+        loaded = DurationModel.objects.get()
+        self.assertEqual(loaded.field, duration)
+
+
+class TestQuerying(TestCase):
+
+    @classmethod
+    def setUpTestData(cls):
+        cls.objs = [
+            DurationModel.objects.create(field=datetime.timedelta(days=1)),
+            DurationModel.objects.create(field=datetime.timedelta(seconds=1)),
+            DurationModel.objects.create(field=datetime.timedelta(seconds=-1)),
+        ]
+
+    def test_exact(self):
+        self.assertSequenceEqual(
+            DurationModel.objects.filter(field=datetime.timedelta(days=1)),
+            [self.objs[0]]
+        )
+
+    def test_gt(self):
+        self.assertSequenceEqual(
+            DurationModel.objects.filter(field__gt=datetime.timedelta(days=0)),
+            [self.objs[0], self.objs[1]]
+        )
+
+
+class TestSerialization(TestCase):
+    test_data = '[{"fields": {"field": "1 01:00:00"}, "model": "model_fields.durationmodel", "pk": null}]'
+
+    def test_dumping(self):
+        instance = DurationModel(field=datetime.timedelta(days=1, hours=1))
+        data = serializers.serialize('json', [instance])
+        self.assertEqual(json.loads(data), json.loads(self.test_data))
+
+    def test_loading(self):
+        instance = list(serializers.deserialize('json', self.test_data))[0].object
+        self.assertEqual(instance.field, datetime.timedelta(days=1, hours=1))
+
+
+class TestValidation(TestCase):
+
+    def test_invalid_string(self):
+        field = models.DurationField()
+        with self.assertRaises(exceptions.ValidationError) as cm:
+            field.clean('not a datetime', None)
+        self.assertEqual(cm.exception.code, 'invalid')
+        self.assertEqual(
+            cm.exception.message % cm.exception.params,
+            "'not a datetime' value has an invalid format. "
+            "It must be in [DD] [HH:[MM:]]ss[.uuuuuu] format."
+        )

tests/utils_tests/test_dateparse.py

@@ -1,9 +1,9 @@
 from __future__ import unicode_literals
 
-from datetime import date, time, datetime
+from datetime import date, time, datetime, timedelta
 import unittest
 
-from django.utils.dateparse import parse_date, parse_time, parse_datetime
+from django.utils.dateparse import parse_date, parse_time, parse_datetime, parse_duration
 from django.utils.timezone import get_fixed_timezone
 
 
@@ -46,3 +46,43 @@ class DateParseTests(unittest.TestCase):
         # Invalid inputs
         self.assertEqual(parse_datetime('20120423091500'), None)
         self.assertRaises(ValueError, parse_datetime, '2012-04-56T09:15:90')
+
+
+class DurationParseTests(unittest.TestCase):
+    def test_seconds(self):
+        self.assertEqual(parse_duration('30'), timedelta(seconds=30))
+
+    def test_minutes_seconds(self):
+        self.assertEqual(parse_duration('15:30'), timedelta(minutes=15, seconds=30))
+        self.assertEqual(parse_duration('5:30'), timedelta(minutes=5, seconds=30))
+
+    def test_hours_minutes_seconds(self):
+        self.assertEqual(parse_duration('10:15:30'), timedelta(hours=10, minutes=15, seconds=30))
+        self.assertEqual(parse_duration('1:15:30'), timedelta(hours=1, minutes=15, seconds=30))
+        self.assertEqual(parse_duration('100:200:300'), timedelta(hours=100, minutes=200, seconds=300))
+
+    def test_days(self):
+        self.assertEqual(parse_duration('4 15:30'), timedelta(days=4, minutes=15, seconds=30))
+        self.assertEqual(parse_duration('4 10:15:30'), timedelta(days=4, hours=10, minutes=15, seconds=30))
+
+    def test_fractions_of_seconds(self):
+        self.assertEqual(parse_duration('15:30.1'), timedelta(minutes=15, seconds=30, milliseconds=100))
+        self.assertEqual(parse_duration('15:30.01'), timedelta(minutes=15, seconds=30, milliseconds=10))
+        self.assertEqual(parse_duration('15:30.001'), timedelta(minutes=15, seconds=30, milliseconds=1))
+        self.assertEqual(parse_duration('15:30.0001'), timedelta(minutes=15, seconds=30, microseconds=100))
+        self.assertEqual(parse_duration('15:30.00001'), timedelta(minutes=15, seconds=30, microseconds=10))
+        self.assertEqual(parse_duration('15:30.000001'), timedelta(minutes=15, seconds=30, microseconds=1))
+
+    def test_negative(self):
+        self.assertEqual(parse_duration('-4 15:30'), timedelta(days=-4, minutes=15, seconds=30))
+
+    def test_iso_8601(self):
+        self.assertEqual(parse_duration('P4Y'), None)
+        self.assertEqual(parse_duration('P4M'), None)
+        self.assertEqual(parse_duration('P4W'), None)
+        self.assertEqual(parse_duration('P4D'), timedelta(days=4))
+        self.assertEqual(parse_duration('P0.5D'), timedelta(hours=12))
+        self.assertEqual(parse_duration('PT5H'), timedelta(hours=5))
+        self.assertEqual(parse_duration('PT5M'), timedelta(minutes=5))
+        self.assertEqual(parse_duration('PT5S'), timedelta(seconds=5))
+        self.assertEqual(parse_duration('PT0.000005S'), timedelta(microseconds=5))

tests/utils_tests/test_duration.py

@@ -0,0 +1,43 @@
+import datetime
+import unittest
+
+from django.utils.dateparse import parse_duration
+from django.utils.duration import duration_string
+
+
+class TestDurationString(unittest.TestCase):
+
+    def test_simple(self):
+        duration = datetime.timedelta(hours=1, minutes=3, seconds=5)
+        self.assertEqual(duration_string(duration), '01:03:05')
+
+    def test_days(self):
+        duration = datetime.timedelta(days=1, hours=1, minutes=3, seconds=5)
+        self.assertEqual(duration_string(duration), '1 01:03:05')
+
+    def test_microseconds(self):
+        duration = datetime.timedelta(hours=1, minutes=3, seconds=5, microseconds=12345)
+        self.assertEqual(duration_string(duration), '01:03:05.012345')
+
+    def test_negative(self):
+        duration = datetime.timedelta(days=-1, hours=1, minutes=3, seconds=5)
+        self.assertEqual(duration_string(duration), '-1 01:03:05')
+
+
+class TestParseDurationRoundtrip(unittest.TestCase):
+
+    def test_simple(self):
+        duration = datetime.timedelta(hours=1, minutes=3, seconds=5)
+        self.assertEqual(parse_duration(duration_string(duration)), duration)
+
+    def test_days(self):
+        duration = datetime.timedelta(days=1, hours=1, minutes=3, seconds=5)
+        self.assertEqual(parse_duration(duration_string(duration)), duration)
+
+    def test_microseconds(self):
+        duration = datetime.timedelta(hours=1, minutes=3, seconds=5, microseconds=12345)
+        self.assertEqual(parse_duration(duration_string(duration)), duration)
+
+    def test_negative(self):
+        duration = datetime.timedelta(days=-1, hours=1, minutes=3, seconds=5)
+        self.assertEqual(parse_duration(duration_string(duration)), duration)