UTC time to time based by timezone offset - php

Question

I am saving all the times in MySQL in UTC(0), so I could change them later while I'm showing the times for the users with different time zones, for saving into db, I use:
function get_utc(){
date_default_timezone_set('UTC');
return date("Y-m-d H:i:s");
}
$now = get_utc();
And now I want to convert those times into different timezones based by timezones offset, I am using this function:
function utc_and_timezone($utc_time, $offset) {
return date("Y-m-d H:i:s", strtotime($offset, strtotime($utc_time)));
}
So for example, if the UTC time is: 2013-01-30 21:06:29
Applying the +5 timezone on that time is easy to find:
$new_time = utc_and_timezone("2013-01-30 21:06:29", "+5 hours"); // Works Fine
It works JUST fine with offsets like 5,6 or other integers, BUT with some other like +3.5, +2.5 this is not working:
$new_time = utc_and_timezone("2013-01-30 21:06:29", "+5.5 hours"); // NOT WORKING
Anyone knows why?!
Any better solutions for making UTC times in different timezones...?
Thanks
SHORT QUESTION:
I want to show a UTC time like 2013-01-30 21:06:29 in +3.5 timezone, how is that possible?

Answer 1

On the PHP side, you can try:
$utc_time = '2013-01-30 21:06:29';
$offset = '3.5';
echo date("Y-m-d H:i:s", strtotime($utc_time) + (3600 * $offset) );
//Returns 2013-01-31 00:36:29
$utc_time = '2013-01-30 21:06:29';
$offset = '-5.5';
echo date("Y-m-d H:i:s", strtotime($utc_time) + (3600 * $offset) );
//Returns 2013-01-30 15:36:29
On the MySQL side, you can just use CONVERT_TZ:
SELECT CONVERT_TZ('2013-01-30 21:06:29','+00:00','+03:30');
//Returns January, 31 2013 00:56:29+0000
SELECT CONVERT_TZ('2013-01-30 21:06:29','+00:00','-05:50');
//Returns January, 30 2013 15:16:29+0000