Finding out if user is in DST or not?

[Aeiri]

I am currently using this function that I made for getting the time of something.

(Note: $timestamp is a UNIX timestamp variable, and $tz_offset is the timezone offset the user chose that is in a mySQL database)

function func_date($timestamp,$tz_offset){
return gmdate("g:i A l F d, Y",$timestamp+($tz_offset*3600));
}

I was wondering how I would go about changing this to figure out if the user is in DST time, so I can add another 3600 seconds to the input.

Any help would be appreciated, thanks.

EDIT: Oh, and the $tz_offset is a value (-12 through 12) that is represented by the different timezones.

[Weedpacket]

Not really; Daylight Saving is a political decision and as such varies from political territory to political territory (and also within political territories). The only real way of finding out is to ask the user.