[RESOLVED] time calculations

jacksonpt

I'm working on a timing application and am having trouble fine tuning the time calculations.

In a nut shell, I'm timing how long something takes. I record a time stamp at the start, and timestamp at the end, then calculate the difference between the two times.

// $t1 and $t2 are timestamps defined earlier in the code
$starttime = strtotime($t1);
$endtime = strtotime($t2);
$t = $endtime - $starttime;   	// calculates time in seconds
$t = $t / 60;                             // converts to minutes

This is pretty straight forward, and it works. The problem is dealing with remainders. For example...

$t1: 11:37:47
$t2 : 11:45:22

The code above calculates the difference as 7.58333.

How do I take 7.58333 and convert the remainder to seconds (i.e. 7:35)?

bradgrafelman

jacksonpt;10984248 wrote:
How do I take 7.58333 and convert the remainder to seconds (i.e. 7:35)?

If I told you something took 3 minutes to do, how many seconds did it take?

Same process as what you're asking; if something took 0.58333 minutes to do, how many seconds did it take?

As far as PHP functions go, you could split up the fraction portion from the whole number like so:

$decimal_number = 7.58333; // assuming you're starting with this

$fraction_part = $decimal_number - floor($decimal_number);
$whole_part = floor($decimal_number );

Derokorian

Another option (the way I do time calc) is to explode at the decimal:

$time= 7.87323;
list($min,$sec) = explode('.',$time);
$sec = $sec*60;
echo "$min minutes and $sec seconds";

You could floor, ceil, or round the $sec after the calc to get a number without a decimal if you like.

jacksonpt

OK... I think I got it. I was struggling with how to convert a fraction of a minute into whole seconds, i.e. 1.75 minutes into 1 minute 45 seconds.

Thanks for the tips. Separating out the minutes from teh seconds with explode was really helpful.

$starttime = strtotime($t1);
$endtime = strtotime($t2);
$t = $endtime - $starttime;                      // calculates time in seconds
$t = $t / 60;                                              // converts to minutes/seconds
list($min,$sec) = explode('.',$t);               // separates the whole minutes from the remainder
$sec = ($sec * 6) / 10;                             // converts the remainder to seconds
$t = $min . ":" . $sec;                               // puts minutes and seconds back together again
return $t;

bradgrafelman

I don't understand what you're doing here:

$sec = ($sec * 6) / 10;                             // converts the remainder to seconds

So 0.5 minutes is equal to (5 * 6) / 10 seconds, or 0.3 seconds?

Derokorian

$sec = ($sec * 6) / 10;

I believe this math is wrong. If you have .25 minutes times 6 then divided by 10 you get .15 seconds (as opposed to 15). Or if you have .5 minutes times 6 then divided by 10 you get .30 seconds instead of 30!

jacksonpt

bradgrafelman;10984259 wrote:
I don't understand what you're doing here:
$sec = ($sec * 6) / 10;                             // converts the remainder to seconds 
So 0.5 minutes is equal to (5 * 6) / 10 seconds, or 0.3 seconds?

Correct. I caught that after I posted when I did more testing. Rounding to 2 decimal places earlier in the code takes .5 minutes to .05. So that calculation then becomes (50*6)/10, or 30 seconds.

jacksonpt

Derokorian;10984260 wrote:
$sec = ($sec * 6) / 10;
I believe this math is wrong. If you have .25 minutes times 6 then divided by 10 you get .15 seconds (as opposed to 15). Or if you have .5 minutes times 6 then divided by 10 you get .30 seconds instead of 30!

Unless I'm missunderstanding you, it's correct.

assuming .25 minutes, the calculation is (256)/10.
assuming .5 minutes, the calculation is (506)/10 (see previous post about rounding).

bradgrafelman

Any reason you chose such an obfuscated path to get to the result? All it takes is a single multiplication:

0.25 60 = 15
0.5 60 = 30

jacksonpt

New code, just for clarification (and in case this ever turns up in someone else's seach)...

function calc_time($t1,$t2) 
{
	$starttime = strtotime($t1);
	$endtime = strtotime($t2);
	$t = $endtime - $starttime;           // calculates time in seconds
	$t = $t / 60;                                   // rounds to 2 decimal places
	$t = round($t,2);                           // converts to minutes/seconds
	list($min,$sec) = explode('.',$t);    // separates the whole minutes from the remainder
	$sec = ($sec * 6) / 10;                  // converts the remainder to seconds
	$t = $min . ":" . $sec;                    // puts minutes and seconds back together again
	return $t;
}

jacksonpt

bradgrafelman;10984264 wrote:
Any reason you chose such an obfuscated path to get to the result? All it takes is a single multiplication:

0.25 60 = 15
0.5 60 = 30

Because of the way explode works (or at least seems to be working so far in my tests)
list($min,$sec) = explode('.',4.25); // $min=4, $sec=25 not .25

The calculation is always based on a whole number, the decimal point goes away. So using explode to separate the minutes from the seconds, my calculations will never be based on a decimal, always a whole number.

bradgrafelman

jacksonpt wrote:
The calculation is always based on a whole number, the decimal point goes away.

... which is probably why using explode() on a number doesn't make much sense in this context (or any other context I can think of, really). 😉

jacksonpt

Maybe not, but it's more intuitive to me than floor(). I've never used either, so I went with what was easier for me to think through in the code.

bradgrafelman

jacksonpt;10984268 wrote:
Maybe not, but it's more intuitive to me than floor(). I've never used either, so I went with what was easier for me to think through in the code.

Parsing numerical data and generating an ASCII representation of it which then gets split into two pieces (neither one numerical - just ASCII text like "Hello" and "World") which then get parsed and converted back into numerical data.

That sounds "more intuitive" than simply rounding a number down to the nearest whole number?

Yikes. :o