Check if current time is between two times, with the possibility of lapping days

Question

I have a system that accepts user submissions, and upon receiving a submission the system will go through all timeslots to find the appropriate timeslot. The problem is that it needs to be able to check against the start & end times if the end time laps to the next day.

Take the following example: A timeslot begins at 10:30 PM on the current day and ends at 4:00 PM the next day. If the current time is between 10:30 PM and 11:59:59 PM, the submission will be assigned to that timeslot. However, if the current time is between 12:00 AM and 4:00 PM then it will skip the timeslot.

This is what I have so far:

function check_time($from, $to, $time) {
    $time = strtotime($time);
    $from = strtotime($from);
    $to_ = strtotime($to);
    $to = $to_ <= $from ? strtotime($to . " tomorrow") : $to_;
    return ($time >= $from && $time <= $to);
}

$timeslots = array(
    array("16:00:00", "22:30:00"),
    array("22:30:00", "16:00:00")
);
foreach ($timeslots as $slot) {
    if (check_time($slot[0], $slot[1], date("H:i:s")))
        {
            echo "true\n";
        }
    else 
        {
            echo "false\n";     
        }
}

If the current time is 23:00:00, then the result would be

false
true

But if the current time is 12:00:00 then the result would be

false
false

even though it's technically between the two times.

I know it has to do with the fact that if it's a new day, then the strtotime result for $from will be later in the day. So instead of checking for 10:30 PM yesterday, it checks for 10:30 PM tonight.

My problem is that I cannot seem to come up with a way to make the $from time switch to the previous day if it needs to, similar to how I force the $to time into the next day.

Answer 1

This is much easier than you expect. Assume that you have three times, t1, t2 and tn which represent from, to and user time respectively. Treat these times as six digit numbers (from 000000 to 235959) and check:

• If t1 and t2 are present on the same side of midnight boundary
  • Check if tn lies between t1 and t2
• Else
  • Check if tn does not lie between t2 and t1

Code and tests:

function check_time($t1, $t2, $tn) {
    $t1 = +str_replace(":", "", $t1);
    $t2 = +str_replace(":", "", $t2);
    $tn = +str_replace(":", "", $tn);
    if ($t2 >= $t1) {
        return $t1 <= $tn && $tn < $t2;
    } else {
        return ! ($t2 <= $tn && $tn < $t1);
    }
}
$tests = array(
    array("16:00:00", "22:30:00", "15:00:00"),
    array("16:00:00", "22:30:00", "16:00:00"),
    array("16:00:00", "22:30:00", "22:29:59"),
    array("16:00:00", "22:30:00", "22:30:00"),
    array("16:00:00", "22:30:00", "23:59:59"),
    array("22:30:00", "16:00:00", "22:29:59"),
    array("22:30:00", "16:00:00", "22:30:00"),
    array("22:30:00", "16:00:00", "15:59:59"),
    array("22:30:00", "16:00:00", "16:00:00"),
    array("22:30:00", "16:00:00", "17:00:00")
);
foreach($tests as $test) {
    list($t1, $t2, $t0) = $test;
    echo "$t1 - $t2 contains $t0: " . (check_time($t1, $t2, $t0) ? "yes" : "no") . "\n";
}
// OUTPUT
//
// 16:00:00 - 22:30:00 contains 15:00:00: no
// 16:00:00 - 22:30:00 contains 16:00:00: yes
// 16:00:00 - 22:30:00 contains 22:29:59: yes
// 16:00:00 - 22:30:00 contains 22:30:00: no
// 16:00:00 - 22:30:00 contains 23:59:59: no
// 22:30:00 - 16:00:00 contains 22:29:59: no
// 22:30:00 - 16:00:00 contains 22:30:00: yes
// 22:30:00 - 16:00:00 contains 15:59:59: yes
// 22:30:00 - 16:00:00 contains 16:00:00: no
// 22:30:00 - 16:00:00 contains 17:00:00: no