Forum OpenACS Development: Timezones

I'm trying to figure out what the best design is here. There are at least three different timezones in play.

1) Server OS timezone. I don't think we care about this.

2) OACS system timezone setting: The default timezone.

3) User preference: The timezone you're in.

The ACS Java design doc suggests that we store date/times in the DB in the OACS system timezone (2), and then convert to the user's local timezone as appropriate. I think that's a good plan.

My question is: Can the people the procs 'lc_time_utc_to_locale' and 'lc_time_local_to_utc' explain to me how they were supposed to be used?

What I'll need to do is to convert from OACS system timezone setting to user setting and back, so what I really need is 'lc_time_system_to_user' and 'lc_time_user_to_system' procs.

Were these procs designed with a different design in mind?

/Lars

I guess it was Ash Katwala and I that inflicted those procs on the world.  One point is that I disagree with the ACS Java docs (and agree with Eduardo) that date/times should be UTC in the DB (although I also think the server should be on UTC as well so in some sense it is the same answer).  Unfortunately we rely on the DB datetime formatting all over the place
which means running everything as UTC and formatting on
output is problematic.

Anyway, those routines were the lowest level ones on which
something like lc_time_utc_to_user would be built.

Also, keep in mind that in some cases you want the time you
present to be something other than the users timezone.
An example would be a travel itenerary where the departure
times should be the local timezone for the airport.

Jon,

I don't think you're missing anything.

I'm just trying to figure out how to do this bastard thing, so I'm asking around.

I'm aware of the timezone package in ref-timezones, which is also what the procs I mentioned in acs-lang use. We want a Tcl API on top of that, though, and that's what the acs-lang procs provide. ref-timezones doesn't have any Tcl API.

The issue of whether server time is UTC or not is still muddy to me. I happen to have no idea whether my server's time is set in UTC or not. When I say 'date' I get my local time. When I say 'date -u', I get UTC time. So far so good, but what it's running internally, I don't know.

How do I find out? How do I set it to UTC if it's not? And do we really want to *require* that *every* server ever running OpenACS must have its internal clock set to UTC?

So if the server's time isn't UTC, should we still store datetimes in UTC? I suppose you would all argue yes here, and I don't have a problem with that.

The other two issues are:

1) I'd like to not require that everybody installs ref-timezones in order to run OpenACS, since it's so big. It should be possible to run a single-timezone site without it.

So either everything should be written so it works without ref-timezones (it seems to be already), or we need to split ref-timezones into a small and a large package somehow. Recommendations here would be welcome.

2) This will require that we run through each and every piece of code in the system that either inputs or outputs a date/time and change them. That's a lot of work. Do you have any good ideas for how to go about this, or is it just grunt, grunt, grunt?

/Lars

One other small gotcha is that if you use MTS with oracle
you need to make sure the listener is started with TZ=GMT
as well.

1) Split table definitions from data. That way we can reference the tables, and still run a single-timezone site without timezone info.

2) Split highly populated timezones from lighly populated ones. This would favor some people over others, though, and I don't particularly like that.

I think I'd prefer 1.