Converting To And From Decimal Time In PHP

Published by philipnorton42 on Mon, 11/29/2010 - 14:00

To convert a time value into a decimal value representing the number of minutes can be useful for certain calculations. The following function takes a time as a string of hh:mm:ss and returns a decimal value in minutes.

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/**
 * Convert time into decimal time.
 *
 * @param string $time The time to convert
 *
 * @return integer The time as a decimal value.
 */
function time_to_decimal($time) {
    $timeArr = explode(':', $time);
    $decTime = ($timeArr[0]*60) + ($timeArr[1]) + ($timeArr[2]/60);
 
    return $decTime;
}

If we take the time of 11:11:11 this gets split into 3 parts by the explode() function into hours, minutes and seconds, which then gets treated in the following way:

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Minutes = (Hours x 60) + (Minutes) + (Seconds / 60)
Minutes = (11 x 60) + (11) + (11 / 60)
Minutes = (660) + (11) + (0.18333333)
Minutes = 671.18333333

The function can be used as follows:

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echo time_to_decimal("11:11:11"); // prints 671.18333333

The reverse of this function takes the decimal value and returns a string in the format hh:mm:ss.

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/**
 * Convert decimal time into time in the format hh:mm:ss
 *
 * @param integer The time as a decimal value.
 *
 * @return string $time The converted time value.
 */
function decimal_to_time($decimal) {
    $hours = floor($decimal / 60);
    $minutes = floor($decimal % / 60);
    $seconds = $decimal - (int)$decimal;
    $seconds = round($seconds * 60);
 
    return str_pad($hours, 2, "0", STR_PAD_LEFT) . ":" . str_pad($minutes, 2, "0", STR_PAD_LEFT) . ":" . str_pad($seconds, 2, "0", STR_PAD_LEFT);
}

This function can be used as follows:

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echo decimal_to_time(671.18333333); // prints 11:11:11

Note that these functions deal with amounts of time, not the time of day. Converting between time and decimal time of day requires a different set of calculations.

UPDATE: Thanks to an anonymous poster for pointing out some errors, these have now been corrected.

Category: 
PHP
Tags: 
PHP
time
decimal

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Comments

Anonymous (not verified) - Mon, 10/03/2011 - 20:32

Hi Philip,

Your code indeed works in the manner you have described, however there are a couple of finer details that caused issues for me when using the code.

In the time_to_decimal function, line 12 should read as follows:

$decTime = ($timeArr[0]*60) + ($timeArr[1]) + ($timeArr[2]/60); >

As it is written in your post, the seconds are actually representing fractions of an hour (1/3600th) as opposed to fractions of a minute (1/60th). 

We have the same issue in the decimal_to_time function as well as an issue in regards to the round() function.  I've corrected the decimal_to_time function as follows:

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function decimal_to_time($decimal) {
    $hours = floor((int)$decimal / 60);
    $minutes = floor((int)$decimal % 60);
    $seconds = $decimal - (int)$decimal; 
    $seconds = round($seconds * 60); 
 
    return str_pad($hours, 2, "0", STR_PAD_LEFT) . ":" . str_pad($minutes, 2, "0", STR_PAD_LEFT) . ":" . str_pad($seconds, 2, "0", STR_PAD_LEFT);
}

round() in lines 2 and 3 have been replaced by floor().  This is due to the behavior of round() returning 1 when given .5.  An example is as follows:

Say we are converting 1:30:30 into a decimal representing minutes.  Using the two functions posted we would have

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echo time_to_decimal('1:30:30'); // prints 90.008333333333, seconds are still converted incorrectly
 
// this should display the input from the first function
echo decimal_to_time(90.008333333333); // prints 02:02:30, not correct

In the example, line 2 of the original code calculates to - round( 90 / 60 ) = round(1.5) = 2.  Since we only want the numer of whole hours in the $decimal variable, we should use floor() instead.  floor() will always round to the lowest whole number ( 1 in this case )

I hope this helps someone out there :)

philipnorton42's picture

philipnorton42 - Mon, 10/03/2011 - 20:55

Thank you for all the hard work you put into that comment! I really appreciate it when a user posts such detailed comments on this blog :)

I have tested your examples and updated my code accordingly.

Anonymous (not verified) - Sun, 12/18/2011 - 20:45

hi tae, thanks..

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