Different timezones have the same timestamp?

Question

I ran this script:

echo date_default_timezone_get()."\n";
echo "----\n";

date_default_timezone_set('Asia/Kabul');
echo date_default_timezone_get()."\n";
echo "----\n";

echo time()."\n";
$dt = new DateTime;
echo $dt->format('U') . "\n";
echo "----\n";

date_default_timezone_set('UTC');
echo date_default_timezone_get()."\n";
echo "----\n";

echo time()."\n";
$dt = new DateTime;
echo $dt->format('U') . "\n";

and for all the 4 timestamp values, it says: 1325905766.

I read somewhere that new DateTime always sets UTC as timezone, whatever the timezone setting, so I get that, but what about time()?

A few seconds before, on a different server (probably not in Europe (ideone.com)), it returns 4 times: 1325905723.

That's the same! (A few seconds diff obviously, but the same timezone.)

time() always and only returns UTC??? What's going on??

I just ran into a similar problem not long ago. I was trying to set the timezone on a per-user basis (via a setting in the profile), but all it would change via the date() function was the timezone identifier at the end. It wasn't actually changing the time itself. — animuson
possible duplicate of Does PHP time() return a GMT/UTC Timestamp? — deceze

jwodder jwodder · Accepted Answer · 2012-01-07T03:16:48

Yes, they both use UTC. Specifically, both time() and the U format return the number of non-leap seconds elapsed since midnight UTC on January 1, 1970 (the "Unix epoch"). As the epoch is a fixed point whose definition is independent of the user's timezone, and as the number of seconds since then is the same in all time zones (ignoring relativistic effects and whatnot), time() returns the same value regardless of time zone settings.

Different timezones have the same timestamp?

2 Answers