html5datetime.py

from django.template import Library

register = Library()

@register.filter_function
def html5datetime(date):
    """Format a date or a date and time according to the HTML 5 specifications,
    so it may be used as the value for a datetime attribute of a time tag.

    Most of the date formatting could be done in the template with the built-in 
    date filter, but HTML 5 requires the time-zone offset to be in the format 
    HH:MM, and this is not possible to do with the built-in filter.

    See http://www.whatwg.org/specs/web-apps/current-work/multipage/common-microsyntaxes.html#valid-global-date-and-time-string

    >>> import datetime
    >>> date = datetime.datetime(2009, 10, 31, 16, 4, 17, 428896)
    >>> print html5datetime(date) # doctest:+ELLIPSIS
    2009-10-31T16:04:17...:...

    >>> print html5datetime(date.date())
    2009-10-31
    """
    import re
    from django.utils.dateformat import DateFormat

    # If this is just a date and not a datetime, we can just 
    # return return the date as YYYY-MM-DD and don't have to
    # worry about the extra requirements of the HTML 5 specs.
    if not hasattr(date, 'hour'):
        return date.strftime('%Y-%m-%d')

    formatter = DateFormat(date)
    offset = formatter.O()

    match = re.match(r'(?P<start>[-+]\d\d)(?P<end>\d\d)', offset)

    if not match:
        return ''

    return date.strftime('%Y-%m-%dT%H:%M:%S%%s') % ':'.join(match.groups())