PHP рассчитайте разницу в датах
//get Date diff as intervals
$d1 = new DateTime("2018-01-10 00:00:00");
$d2 = new DateTime("2019-05-18 01:23:45");
$interval = $d1->diff($d2);
$diffInSeconds = $interval->s; //45
$diffInMinutes = $interval->i; //23
$diffInHours = $interval->h; //8
$diffInDays = $interval->d; //21
$diffInMonths = $interval->m; //4
$diffInYears = $interval->y; //1
//or get Date difference as total difference
$d1 = strtotime("2018-01-10 00:00:00");
$d2 = strtotime("2019-05-18 01:23:45");
$totalSecondsDiff = abs($d1-$d2); //42600225
$totalMinutesDiff = $totalSecondsDiff/60; //710003.75
$totalHoursDiff = $totalSecondsDiff/60/60;//11833.39
$totalDaysDiff = $totalSecondsDiff/60/60/24; //493.05
$totalMonthsDiff = $totalSecondsDiff/60/60/24/30; //16.43
$totalYearsDiff = $totalSecondsDiff/60/60/24/365; //1.35
Grepper