Everyday Calculation

Free calculators and unit converters for general and everyday use.

Calculators » Date & Time » Clock Time Calculator

Time Calculator - Add/ Subtract

Our online tools will provide quick answers to your calculation and conversion needs. On this page, you can add/ subtract any number of hours or minutes to/ from a given clock time. Get answer to questions like "what time will it be in 8 hours?" "what time was it 45 minutes ago?"

Enter time as hh:mm e.g., 03:30 AM

hh mm

Result window

To find hours between two time values, use our time duration calculator.

To add two or more time-intervals, use our timesheet calculator.

Download: Use this time calculator offline with our all-in-one calculator app for Android and iOS.

Time Calculation

Before we start the calculation, we convert the time value to 24-hour format.

Steps for adding time

e.g., what time will it be in 30 minutes?
Add the hours and the minutes separately. If the minutes are >= 60, subtract 60 from the minutes and add 1 to hours. If the hours are >= 24, set hours to "hours mod 24".

Steps for subtracting time

e.g., what time was it 16 hours ago?
Subtract the hours and the minutes separately. If the minutes are <= 0, add 60 to the minutes and subtract 1 from hours. If the hours are <= 0, add 24 and set it to "hours mod 24".

Convert the time back to 12-hour format at the end of calculation.

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