[RESOLVED] Problem with subtracting times.

[dv6cougar]

Hello 🙂

I have a script where the purpose is to subtract my hours at work from one another, to find out how many hours i actually worked that day.

Here's my script:

function sub_time($time1, $time2, $month, $day, $year) {

		//first get the minutes and hours of time 1 and 2
			$time_start = explode(":", $time2);

			$time_stop = explode(":", $time1);

		//now convert the time...

			$start1 = mktime($time_start[0], $time_start[1], 0, $month, $day, $year);
			$stop1 = mktime($time_stop[0], $time_stop[1], 0, $month, $day, $year);


			$newtime = ($stop1 - $start1);

		   return date('h:i', $newtime);

	}

Now for use we could say:

$getTimer[$i] = sub_time("20:15", "9:30","10","5","1999");

this returns: 11:45 - which is incorrect.. it actually should be 10:45. Now i have searched and searched the net and here for an answer without luck 🙂, I even played with it myself and put in somecode that checks if the minutes are set and if they are to subtract an hour from the hours, before displaying it.

However, it is only in some cases that it actually is missing an hour - not all. For exampled:

$getTimer[$i] = sub_time("20:00", "10:00","10","5","1999");

this does correctly return 10.

$getTimer[$i] = sub_time("20:15", "10:00","10","5","1999");

this also correctly returns 10:15 - now I'm a bit confused... Anyone that can see a problem with my code 🙂?

i realize month by the way that month, day and year is a bit over the edge here, but is used in a different part of the script. 🙂

Thanks in advance 🙂

[Weedpacket]

dv6cougar wrote:

this returns: 11:45 - which is incorrect.. it actually should be 10:45.

I get 10:45. If I change the local timezone the result can range between 1:15 (Marquesas) and 12:45 (thirty-five hits, from Blantyre in Malawi to Tahiti). Copenhagen is one of those that gives 11:45.

After all, in the last line of your function what you're returning is whatever local time was at 22:45 GMT on January 1 1970 (using a 12-hour clock). In other words, at that point you forget that what you have is a duration and try to use it as a timestamp.

[bpat1434]

Let's look at what you're doing. You're taking two timestamps which are nothing but number of seconds since Unix Epoch and subtracting them. So the difference that's left is the total number of seconds between the two times, not a unix timestamp. The date function expects a timestamp, not an integer value equating to the number of seconds between two times.

Your function would be better served to do individual calculations. Since you're dealing with just one days time period, you can simply do something like:

function subTime($start, $end, $m, $d, $y)
{
        $start = strtotime("$m/$d/$y $start");
        $end = strtotime("$m/$d/$y $end");

    $diff = $end-$start;

    $hours = floor($diff/3600); // 60 seconds * 60 minutes
    $diff -= $hours*3600;

    $mins = floor($diff/60); // 60 seconds
    $diff -= $mins*60;

    $secs = $diff;

    echo $hours.':'.$mins.':'.$secs;
}

[dv6cougar]

Hey.. thanks for your help.

Offcourse it makes alot more sense now, what in the world was i thinking 😉.