[kronolith] Re: [horde] kronolith: adjusting for user vs. system time zone

[Chuck Hagenbuch]

Quoting Mark Bennett <bennettm+horde at mailsnare.net>:

> Unless I?m missing something (which is entirely possible), it appears 
> that the
> kronolith alarms assume that the user?s time zone preference is the same as
> the system clock. For example, we run all of our systems in UTC but 
> most users
> will set their preference to their local time zone. As a result, events that
> should be generating reminders do not because kronolith is comparing 
> everything against the system time.

Yeah. See http://bugs.horde.org/ticket/?id=1088

> One solution that we?ve been experimenting with is a patch to
> lib/Kronolith.php that converst the system time to the user?s local time
> before calling the $kronolith->listAlarms. That allows an apple-to-apple
> comparison when looking for events that need to trigger a reminder.
>
> The kronolith storage drivers (at least the sql one) is pulling in possible
> events from the current day to the current date + 1. Depending on the user?s
> time zone, the system date could be a day ahead or a day behind the user, so
> you really need to look at day-1 to day+1.
>
> I?ve roughed-in some code changes in our test environment to test this
> approach and it seems to work well enough but wanted to get some feedback
> before I offered up a patch. I?m sure there might be a more elegant approach
> or maybe some other code dependency.

This is something that ought to be solved in general, not just for 
alarms; there
are questions about what should happen when users change their time zone, etc.

It has been suggested before that we should store all times as UTC in the
backend and convert from there. The complication with that is that there are
some events that always happen at 9am for whatever timezone you're in, 
and some
that should change - perhaps giving events an optional timezone field would
solve that? And of course some pretty robust conversion scripts, probably with
an option to either give events the server's timezone or the user's, would be
needed.

This should probably move to the kronolith list, btw, which I've cc'ed 
- please
direct future posts there, and drop the horde list from replies.

-chuck

-- 
"But she goes not abroad in search of monsters to destroy." - John 
Quincy Adams