How to make now() and different timezones get along

[kenji776]

As my title and summary suggest, I just started using the now function, mainly
for keeping track of when users last logged in. The question is, how can I make
now work with different timezones. I know that I should have a field that users
specify what one they are in, then how do I use that with the now() function,
or something equivilant. Bascially I want to be able to tell what time it is,
anywhere in the world, easily, once users have specified what time zone they
are in so I can keep track of the last time they logged in and a few other
things.

[PaulH]

see
[url]http://www.macromedia.com/cfusion/webforums/forum/messageview.cfm?catid=3&thread[/url]
id=1027652&CFID=145465&CFTOKEN=989eca8c3946cc3f-2B093B57-02FD-D9B2-E90C13A3EF684
AF3&jsessionid=48304c83e49f7e266472 thread.

[kenji776]

wow that page that you linked in the thread that you told me to is really cool.
Just why are there so many timezones? Its crazy! Overall that should probobly
do what i want it to... if i can figure out how to use that cfc, i havn't
looked at it yet.Thanks a bunch, hopefully i can get that to work for me.

[PaulH]

because politicians control timezones. some places use DST, some don't. soem
sop/start DST different from surrounding areas. some of the timezones are
actually historical. also so many are included because its easy for people to
recognize their city/region rather than a UTC offset, etc.

[kenji776]

Okay makes sence. Now then, im just a stupid kid trying to code this all, so
can you maybe give me a quick example on how i would go about using your cfc?
Say for instance I have a form field called form.timezone, a database field
called timezone, and a database field called last_logged_in that automatically
gets set each time someone logs in, using the now() function. How could I
incorperate your cfc to do what i need it to? Any help here is appreciated.
Thanks!

[PaulH]

first off store your dates (note that you need a datetime not just a time) in a
single timezone (tz), UTC is usually a good choice.

<cfset tz=createObject("component","timeZone")> <!--- or wherever the CFC is
located --->
<cfquery name="getLogin" datasource="dsn">
SELECT last_logged_in,timezone
FROM someTable
WHERE user='#form.user#'
</cfquery>

<cfoutput>
#dateFormat(tz.castFromUTC(last_logged_in,timezone ))#
#timeFormat(tz.castFromUTC(last_logged_in,timezone ))#
</cfoutput>

[kenji776]

Wow, timezones are confusing. I am suprised cold fusion doesn't have a built in
way to handle this, or a way to get the time from the users computer or
something, because this is crazyness. Thanks a bunch paul... but it looks like
this is a little over my head for the time being.

[PaulH]

no, that's not crazy, that's just the way the world is. you might have a look
at [url]http://www.sustainablegis.com/tips/getClientTZ.cfm[/url]. it only works w/ie 6.0
and above (though the actual js gateway should be able to work w/firefox,
etc.).

[kenji776]

Hmm that does look neat however it doesn't seem to work in firefox. I guess I
should try and do some more reaserach into how the UTC works before I try and
do things involving it. BTW you component really looks like it rocks, nice work
with that, I hope i can figure enough out to be able to use it in my site.
Again thanks for the help.

[PaulH]

as i said i think that gateway should work, just that i wrote that bit for ie. you might contact the author (dan) about the gateway.