1   Pattern Syntax

While Babel makes it simple to use the appropriate date/time format for a given locale, you can also force it to use custom patterns. Note that Babel uses different patterns for specifying number and date formats compared to the Python equivalents (such as time.strftime()), which have mostly been inherited from C and POSIX. The patterns used in Babel are based on the Locale Data Markup Language specification (LDML), which defines them as follows:

A date/time pattern is a string of characters, where specific strings of characters are replaced with date and time data from a calendar when formatting or used to generate data for a calendar when parsing. […]

Characters may be used multiple times. For example, if y is used for the year, yy might produce "99", whereas yyyy produces "1999". For most numerical fields, the number of characters specifies the field width. For example, if h is the hour, h might produce "5", but hh produces "05". For some characters, the count specifies whether an abbreviated or full form should be used […]

Two single quotes represent a literal single quote, either inside or outside single quotes. Text within single quotes is not interpreted in any way (except for two adjacent single quotes).

For example:

.. code-block:: pycon

    >>> d = date(2007, 4, 1)
    >>> format_date(d, "EEE, MMM d, ''yy", locale='en')
    u"Sun, Apr 1, '07"
    >>> format_date(d, "EEEE, d.M.yyyy", locale='de')
    u'Sonntag, 1.4.2007'

    >>> t = time(15, 30)
    >>> format_time(t, "hh 'o''clock' a", locale='en')
    u"03 o'clock PM"
    >>> format_time(t, 'H:mm a', locale='de')
    u'15:30 nachm.'

    >>> dt = datetime(2007, 4, 1, 15, 30)
    >>> format_datetime(dt, "yyyyy.MMMM.dd GGG hh:mm a", locale='en')
    u'02007.April.01 AD 03:30 PM'

The syntax for custom datetime format patterns is described in detail in the the Locale Data Markup Language specification. The following table is just a relatively brief overview.

2   Time-zone Support

Many of the verbose time formats include the time-zone, but time-zone information is not by default available for the Python datetime and time objects. The standard library includes only the abstract tzinfo class, which you need appropriate implementations for to actually use in your application. Babel includes a tzinfo implementation for UTC (Universal Time).

For real time-zone support, it is strongly recommended that you use the third-party package pytz, which includes the definitions of practically all of the time-zones used on the world, as well as important functions for reliably converting from UTC to local time, and vice versa:

.. code-block:: pycon

    >>> from datetime import time
    >>> from pytz import timezone, utc
    >>> dt = datetime(2007, 04, 01, 15, 30, tzinfo=utc)
    >>> eastern = timezone('US/Eastern')
    >>> format_datetime(dt, 'H:mm Z', tzinfo=eastern, locale='en_US')
    u'11:30 -0400'

The recommended approach to deal with different time-zones in a Python application is to always use UTC internally, and only convert from/to the users time-zone when accepting user input and displaying date/time data, respectively. You can use Babel together with pytz to apply a time-zone to any datetime or time object for display, leaving the original information unchanged:

.. code-block:: pycon

    >>> british = timezone('Europe/London')
    >>> format_datetime(dt, 'H:mm zzzz', tzinfo=british, locale='en_US')
    u'16:30 British Summer Time'

Here, the given UTC time is adjusted to the "Europe/London" time-zone, and daylight savings time is taken into account. Daylight savings time is also applied to format_time, but because the actual date is unknown in that case, the current day is assumed to determine whether DST or standard time should be used.

.. code-block:: pycon

    >>> from pytz import timezone
    >>> from babel import Locale
    >>> from babel.dates import get_timezone_name

    >>> tz = timezone('Europe/Berlin')
    >>> get_timezone_name(tz, locale=Locale.parse('pt_PT'))
    u'Hor\xe1rio Alemanha'

.. code-block:: pycon

    >>> from datetime import datetime

    >>> dt = tz.localize(datetime(2007, 8, 15))
    >>> get_timezone_name(dt, locale=Locale.parse('de_DE'))
    u'Mitteleurop\xe4ische Sommerzeit'
    >>> get_timezone_name(tz, locale=Locale.parse('de_DE'))
    u'Deutschland'

3   Parsing Dates

Babel can also parse date and time information in a locale-sensitive manner:

.. code-block:: pycon

    >>> from babel.dates import parse_date, parse_datetime, parse_time