Date Time
Time Calculator
Add hours and minutes to a starting date/time.
Free to use — no sign-up or login.
Result
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The time calculator starts from a date and time you choose, then adds a signed number of hours and a signed number of minutes. Use a negative minute count to step backward. The result includes the weekday and the 24-hour clock time.
To measure the gap between two times you already know, use the Hours Calculator. To rewrite 2:30 PM as 14:30, use the 24-hour clock.
Hours and minutes are separate fields
2 hours and 30 minutes is not typed as 2.5 in a single box. The minute field can be negative, so 09:40 minus 15 minutes is a minute offset of −15 with hours left at 0. The calendar date rolls when the sum crosses midnight.
The start is not “now” unless you set it
The default start is the current minute only so the form is not empty. Change it when the shift, the flight, or the timer should begin at another moment. This page does not lock the start to the live clock.
Worked example: 09:40 plus 2 hours 30 minutes
Start at 13 November 2026 09:40. Add 2 hours and 30 minutes. The result is Friday, 2026-11-13 12:10.
\[ 09{:}40+2\,\mathrm{h}+30\,\mathrm{min} \]
Frequently asked questions
Can minutes be negative?
Yes. A negative minute count steps backward from the start. Hours can be negative too.
What happens after midnight?
The date moves to the next day, or the previous day if the offset is negative, and the weekday changes with it.
Is 2.5 hours the same as 2 hours and 30 minutes?
Enter 2 in hours and 30 in minutes. The form does not ask you to convert the half hour into a decimal.
Does this tell me the gap between two clocks?
No. The Hours Calculator takes a start and an end and reports the span.
Which time zone is used?
The date and time you type are read as local values. The page does not convert cities.
References
Assumptions and limitations
The page adds hours and minutes to one start. It does not compute the span between two times or convert time zones.