<?php
// function to get time
// for another time zone
// given a specific timestamp and hour offset from GMT

function getLocalTime($ts, $offset) {
// performs conversion
// returns UNIX timestamp
return ($ts - date("Z", $ts)) + (3600 * $offset);
}
// get current local time in Singapore
// result: "00:11:26 31-10-06 SST"
echo date("H:i:s d-m-y", getLocalTime(mktime(), 8)) . " SST \n";
// get current local time in India
// result: "21:41:26 30-10-06 IST"
echo date("H:i:s d-m-y", getLocalTime(mktime(), +5.5)) . " IST \n";
// get current local time in USA (Eastern)
// result: "11:11:26 30-10-06 EST"
echo date("H:i:s d-m-y", getLocalTime(mktime(), -5)) . " EST \n";
// get current local time in USA (Pacific)
// result: "08:11:26 30-10-06 PST"
echo date("H:i:s d-m-y", getLocalTime(mktime(), -8)) . " PST \n";
// get time in GMT
// when it is 04:30 AM in India
// result: "23:00:00 01-02-05 GMT "
echo date("H:i:s d-m-y", getLocalTime(mktime(4,30,0,2,2,2005), 0)) .?
" GMT \n";
?>

Phút qua giờ:

<?php
// define number of minutes
$mm = 156;
// convert to hh:mm format
// result: "02h 36m"
echo sprintf("%02dh %02dm", floor($mm/60), $mm%60);
?>

Ngược lại:

<?php
// define hours and minutes
$hhmm = "02:36";
// convert to minutes
// result: "156 minutes"
$arr = explode(":", $hhmm);
echo $arr[0]*60 + $arr[1] . " minutes";
?>

<?php
// create timestamps for two dates
$date1 = mktime(0,0,0,2,1,2007);
$date2 = mktime(1,0,0,2,1,2007);
// compare timestamps
// to see which represents an earlier date
if ($date1 > $date2) {
$str = date ("d-M-Y H:i:s", $date2) . " comes before " .?
date ("d-M-Y H:i:s", $date1);
} else if ($date2 > $date1) {
$str = date ("d-M-Y H:i:s", $date1) . " comes before " .?
date ("d-M-Y H:i:s", $date2);
} else {
$str = "Dates are equal";
}
// result: "01-Feb-2007 00:00:00 comes before 01-Feb-2007 01:00:00"
echo $str;
?>

//FUNCTION FOR TIME LEFT
function time_left($integer)
{

$seconds=$integer;

if ($seconds/60 >=1)

{

$minutes=floor($seconds/60);

if ($minutes/60 >= 1)

{ # Hours

$hours=floor($minutes/60);

if ($hours/24 >= 1)

{ #days

$days=floor($hours/24);

if ($days/7 >=1)

{ #weeks

$weeks=floor($days/7);

if ($weeks>=2) $return="$weeks Weeks";

else $return="$weeks Week";

} #end of weeks

$days=$days-(floor($days/7))*7;

if ($weeks>=1 && $days >=1) $return="$return, ";

if ($days >=2) $return="$return $days days";

if ($days ==1) $return="$return $days day";

} #end of days

$hours=$hours-(floor($hours/24))*24;

if ($days>=1 && $hours >=1) $return="$return, ";

if ($hours >=2) $return="$return $hours hours";

if ($hours ==1) $return="$return $hours hour";

} #end of Hours

$minutes=$minutes-(floor($minutes/60))*60;

if ($hours>=1 && $minutes >=1) $return="$return, ";

if ($minutes >=2) $return="$return $minutes minutes";

if ($minutes ==1) $return="$return $minutes minute";

} #end of minutes

$seconds=$integer-(floor($integer/60))*60;

if ($minutes>=1 && $seconds >=1) $return="$return, ";

if ($seconds >=2) $return="$return $seconds seconds";

if ($seconds ==1) $return="$return $seconds second";

$return="$return.";

return $return;

}

/* Returns a string of the amount of time the integer (in seconds) refers
to.

$timeleft=time_left(86400);

$timeleft='1 day'.

Will not return anything higher than weeks. False if $integer=0 or fails.

*/

<?php
// create timestamps for two dates
$date1 = mktime(0,0,0,2,1,2007);
$date2 = mktime(1,0,0,2,1,2007);
// compare timestamps
// to see which represents an earlier date
if ($date1 > $date2) {
$str = date ("d-M-Y H:i:s", $date2) . " comes before " .?
date ("d-M-Y H:i:s", $date1);
} else if ($date2 > $date1) {
$str = date ("d-M-Y H:i:s", $date1) . " comes before " .?
date ("d-M-Y H:i:s", $date2);
} else {
$str = "Dates are equal";
}
// result: "01-Feb-2007 00:00:00 comes before 01-Feb-2007 01:00:00"
echo $str;
?>

http://marcgrabanski.com/pages/code/jquery-ui-datepicker