Behavior of <?php echo date("H:i:s", 0);?>

I used :

<?php 
echo date("H:i:s", $var_time_diff);
?>

to construct a time between two dates.. and in my head it was

$var_time_diff = 36000 = display 10:00:00 for 10 hours.

But in fact

<?php echo date("H:i:s", 0);?> 

display 01:00:00 and not 00:00:00.

So we have

$date_a = "18:15:04";
$date_b = "23:15:04";
$diff = strtotime($date_b) - strtotime($date_a);

All is ok for the moment $diff is 5 hours but if we display date like this:

echo date("H:i:s", $diff);

it will be "06:00:00".

So something wrong with my php 开发者_开发百科config or it's a normal behavior for php function date?

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The date() function uses your current time zone. If you want to ignore your configured time zone, use date_default_timezone_set() or use gmdate().

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You're in some timezone other than UTC. Try:

<?php
date_default_timezone_set('UTC');
echo date("H:i:s",0) . "\n";

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I'm not sure why, but date outputs the current hour in your example, make a timestamp from your seconds first and it works. I'll be following this question for a deeper explanation though.

$date_a = "18:15:04";
$date_b = "23:15:04";
$diff = strtotime($date_b) - strtotime($date_a);
echo date("H:i:s", mktime(0,0,$diff));

edit: ah, so it adjusts to your current timezone, so does mktime, so the effect is negated.

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use mktime, and min 1 for hour @ $diff