This free time calculator can add or subtract time values in terms of days, hours, minutes, and seconds. You can also add or subtract time intervals directly from any starting calendar date and time.
Time measurement relies on a mixed radix system known as the sexagesimal system (base 60), which traces back thousands of years to ancient Sumer and Babylonia. While human counting predominantly uses base 10 (decimal), base 60 was chosen because 60 is divisible by 1, 2, 3, 4, 5, 6, 10, 12, 15, 20, and 30, making fractional division exceptionally clean.
• 1 Minute = 60 Seconds
• 1 Hour = 60 Minutes = 3,600 Seconds
• 1 Day = 24 Hours = 1,440 Minutes = 86,400 Seconds
• 1 Week = 7 Days = 168 Hours = 604,800 Seconds
Add each column (seconds, minutes, hours, days) separately. If seconds exceed 60, divide by 60 and carry the quotient into the minutes column. If minutes exceed 60, carry into the hours column. If hours exceed 24, carry into days.
Subtract each unit. If the top value is smaller than the bottom value, borrow 1 from the next higher column (e.g. 1 minute gives 60 seconds, 1 hour gives 60 minutes, 1 day gives 24 hours).
In the International System of Units (SI), the second is defined by taking the fixed numerical value of the cesium frequency Δν(Cs), the unperturbed ground-state hyperfine transition frequency of the cesium-133 atom, to be 9,192,631,770 hertz (Hz).
For AM hours between 1:00 AM and 11:59 AM, the hour number remains identical. 12:00 AM (midnight) becomes 00:00. For PM hours between 1:00 PM and 11:59 PM, add 12 to the hour (e.g. 8:30 PM is 20:30). 12:00 PM (noon) remains 12:00.
Yes! You can enter decimals (such as 1.5 hours or 0.25 days) and the engine automatically converts and normalizes them into precise whole units of days, hours, minutes, and seconds.