Add or Subtract Time Calculator
Enter a start time and a duration to add or subtract. The calculator returns the new time of day and tells you how many days it shifts forward or back when it crosses midnight.
How to add or subtract time
- Enter the start time as hours and minutes.
- Enter the hours and minutes to add, or switch to subtract.
- Read the new time and any day shift across midnight.
Examples
Add a duration
10:30 plus 2 hours 45 minutes
13:15 on the same day
Frequently asked questions
Does it handle crossing midnight?
Yes. Adding past 24:00 rolls into the next day, and subtracting before 00:00 rolls into the previous day. The day shift is shown.
Can I add more than 24 hours?
Yes. Large durations are supported. The result shows the final time of day and how many whole days it moved.
Does it use a 12 or 24 hour clock?
Input and output use a 24 hour clock, so 1 PM is 13:00. This avoids any AM and PM confusion.
Can I include seconds?
Yes. If you enter seconds for the start time or the duration, the result is shown down to the second.
Is my data private?
Yes. Everything runs in your browser and nothing is uploaded or stored.
Related tools
Time Duration Calculator
Find the duration between two times of day. Enter a start and end time to get hours and minutes, total minutes and decimal hours, including overnight shifts.
Time Ago Formatter
Turn a date or timestamp into friendly relative time like 3 hours ago or in 2 days. Picks the largest unit from minutes to years, with past and future support.
Add to Date
Add or subtract days, weeks, months and years from any date and get the new date. Handles month-end and leap days correctly. Free and instant.
Age Calculator
Calculate your exact age in years, months and days from your date of birth. See your age in total days, weeks and months too. Free and private.
Business Days Calculator
Count working days between two dates or add business days to a date. Skips weekends and any holidays you list. Inclusive counting, instant results.
Countdown Timer
Free online countdown timer. Count down to a target date and time, or run a duration like 25m or 1h 30m. Big live display, presets, and sound.