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DateRecurringIndex (1.0)

by Olha Pelishok last modified 2009-04-16
Released on 2009-04-16 by Jens Klein for Plone 2.5, Plone 3.0 under GPL - GNU General Public License available for All platforms.
Software development stage: stable
Zope2 index for recurring events. Replacement for old DateIndex.

A Zope 2 catalog index for indexing of recurring events. It can replace the default DatetIndex of Zope 2. It will produce the same results. Therefore and object needs a start attribute.

The DateRecurringIndex takes two additional values into account:

an attribute returning the time in seconds of the interval for the recurring date
an attribute returning the date and time until the recurring should happen.

You can also configure the behaviour on daylight-saving (dst) border change. In short: On change from winter to summer 24h are added. So a recurring date - such as an event - should happen every day 11am. Taken the example day-before + 24h = 12am day after dst change. Usally its not wanted behaviour on human calendars. Therefore you can control this behaviour: adjust, keep and auto. See the recurring.txt doc-test file for detailed information about it. usally on human calendars auto work out fine, on technical calendars keep is the right choice.

Datetime.DateTime vs. datetime.datetime

Inside Zope2 everybody uses DateTime.DateTime or iow the Zope-DateTime. At time of writing Zope-DateTime (around 1998) there was no good date/time implementation in python. But these days - in 2008 - we have a better implementation. Even if the pythons datetime implementation has its problems, together with pytz for timezone handling its very mature.

So, why is it covered here? Just because the above mentioned dst-handling works only if the start and until values are non-naive python datetimes. Just keep it in mind when using this index: If you use recurring dates and you want dst-adjust make sure your implementation returns a python datetime. And also keep in mind: If youre in Austria with CET timezone, add a recuuring date it will looks fine to you, every day at 11:00am, doesnt matter if DST or not, your event happens. If you go international and your event is shown in a different timezone - or in the same in a country without DST at all - it might differ and is not always at the the time.

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