How to add and subtract time
Work from the smallest unit up: add seconds and carry every 60 into a minute, add minutes and carry every 60 into an hour, then carry every 24 hours into a day. Months and years are calendar months: January 31 plus one month is the last day of February.
Nov 3, 2026 + 90 days = Feb 1, 2027
To find the time between two moments, the calculator counts the full days and the hours, minutes and seconds left over, and also shows the total in hours or minutes, which is what you need for a timesheet. For work hours between clock-in and clock-out times, use the hours calculator; to add up a list of durations, the hours and minutes calculator; to count working days, the business days calculator.
Time units
| 1 minute | 60 seconds |
| 1 hour | 60 minutes = 3,600 seconds |
| 1 day | 24 hours = 1,440 minutes |
| 1 week | 7 days = 168 hours |
| 1 month | 28–31 days (30.44 on average) |
| 1 year | 365 days (366 in a leap year) = 8,760 hours |
Time calculator questions
What time will it be in 8 hours?
Add 8 hours to the current time: at 3:00 PM it will be 11:00 PM, and at 7:00 PM it will be 3:00 AM the next day. The calculator starts from your current date and time, so pick “Add or subtract”, enter 8 hours and read the result.
How do I add hours and minutes to a time?
Add the minutes first, carry every 60 minutes into an hour, then add the hours and carry every 24 hours into a day. 9:45 AM + 2 hours 30 minutes = 12:15 PM, because 45 + 30 = 75 minutes = 1 hour 15 minutes.
How many hours are between two dates?
Count the full days between them, multiply by 24 and add the hours left over. From January 1, 9:00 AM to January 3, 5:00 PM is 2 days and 8 hours, or 56 hours. The calculator shows the result in days, hours, minutes and seconds, and as totals.
What date is 90 days from today?
Pick “Add or subtract”, keep today’s date and enter 90 days. Calendar months have 28 to 31 days, so 90 days is about three months but rarely exactly three. For working days only, use the business days calculator.
Does it account for daylight saving time?
No. The calculator uses clock time: adding 24 hours always gives the same time on the next day. On the two nights a year when clocks change, the real elapsed time is one hour more or less.