Question

For example, given the decimal value 5.66, representing 5 hours and 39 minutes, how would I round this number to 5 hours and 45 minutes (the nearest 15 minute interval), aka 5.75.

Similarly, if I had 5 hours and 36 minutes, or 5.6, this is closer to 5:30 than 5:45, so I’d want to get 5.5 out of it.

Trying to write this in PHP.

function round_decimal_time($time, $interval=15){
  // Split up decimal time
  $hours = (int) $time;
  $minutes = $time - $hours;

  // Convert base 10 minutes to base 60 minutes
  $b60_m = $minutes * 60;

  // Round base 60 minutes to nearest interval... (15 minutes by default)
  // DONT KNOW HOW TO DO THIS PART

  // If greater than or equal to 60, go up an hour
  if($b60_m >= 60){
      $hours += 1;
      $minutes = 0;
  } else {
    // Otherwise, convert b60 minutes back into b10
    $time = $hours + ($b60_m / 60);
  }

  return $time;
}

And again, some examples of what I’m trying to do.

Input: 5.66 (5:39 duration)
Output: 5.75

Input: 5.6 (5:36 duration)
Output: 5.50

Input: 5.05 (5:03 duration)
Output: 5.00

Answer 1

Rounding to 'nearest number $X' is done by:

 round($number/$X)*$X;

So, after (0.66 * 60 = 39.6):

 round(39.6/15)*15=45

You can use ceil and floor in a similar manner if you always want to round down or up.

Your total function would be:

 round_decimal_time($time,$round=15){
     return (round($time * 60 / $round) * $round) / 60;
 }