The result will be the new time and date based on the subtracted or added period of time. To calculate the amount of time (days, hours, minutes, seconds) between times on two different dates, use the Time Duration Calculator. Start Time: Hour: millisecond: 10-3 second: microsecond: 10-6 second: nanosecond: 10-9 second: picosecond: 10-12 second: