Showing and setting event date time zones

jensens · May 4, 2020, 9:50am

So @pbauer and @zopyx are both right:

The datetimes are always stored with a timezone. And this is the only valid way to work with dates/datetimes. For recurring dates DST changes need to use the DST associated with the timezone stored with the date, because i.e. in Europe we have different DST boundaries than in US. So, a daily event at 11:00 in Europe would be for some weeks in US at 12 or 10 (depending on) or vice versa.

But the widget/ data converter does not support time zones. It always uses the default timezone

github.com

plone/plone.app.z3cform/blob/master/plone/app/z3cform/converters.py#L106


    return self.field.missing_value
tmp = value.split(' ')
if not tmp[0]:
    return self.field.missing_value
value = tmp[0].split('-')
if len(tmp) == 2 and ':' in tmp[1]:
    value += tmp[1].split(':')
else:
    value += ['00', '00']


# TODO: respect the selected zone from the widget and just fall back
# to default_zone
default_zone = self.widget.default_timezone
zone = default_zone(self.widget.context)\
    if safe_callable(default_zone) else default_zone
ret = datetime(*map(int, value))
if zone:
    tzinfo = pytz.timezone(zone)
    ret = tzinfo.localize(ret)
return ret

The default timezone is either the timezone of the portal, or if set, the timezone property of the currently logged in user:

github.com

plone/plone.app.event/blob/master/plone/app/event/base.py#L426


        query['end'] = {'query': start, 'range': 'min'}
    if end:
        # All events until end date:
        # The maximum start date must be the date until we search.
        query['start'] = {'query': end, 'range': 'max'}
    return query




# TIMEZONE HANDLING


def default_timezone(context=None, as_tzinfo=False):
    """Return the timezone from the portal or user.


    :param context: Optional context. If not given, the current Site is used.
    :type context: Content object


    :param as_tzinfo: Return the default timezone as tzinfo object.
    :type as_tzinfo: boolean


    :returns: Timezone identifier or tzinfo object.
    :rtype: string or tzinfo object

So here is work to be done.

For the output of the date it even gets more complex and is really use-case specific, like show no timezone if there is only one, always show stored timezone, re-calculated to current logged in users timezone, recalculate to browser-selected timezone from request-parameter/cookie (there's nothing suitable by default in the request AFAIK) ... and possibly more.