Time Addition Calculator
Add or subtract hours, minutes, and seconds from a starting time and see the result, even when it rolls past midnight into the next or previous day.
How it works
Pick a starting time, choose whether you're adding or subtracting, and type in the hours, minutes, and seconds you want to shift by. The calculator turns everything into seconds, does the arithmetic, then converts back to a clock time.
When the result lands on a different day, the tool doesn't just silently wrap — it shows a day offset like +1 or −1 so you know the clock time belongs to tomorrow or yesterday. That's the part people usually get wrong by hand.
You get both the 24-hour reading and a plain 12-hour AM/PM version, which is handy whether you're scheduling a shift, timing a cook, or working out an arrival across a long delay.
Frequently asked questions
What happens when the time crosses midnight?
The clock reading wraps around, and a day offset appears next to it. Add four hours to 11 PM and you'll see 3:00 AM with a +1 day note, so the date stays clear.
Can I subtract a duration too?
Yes. Flip the direction to Subtract and the same fields count backwards. Subtracting past midnight shows a −1 day offset rather than pretending the time stayed on the same date.
Does it handle seconds?
It does. All three fields — hours, minutes, and seconds — feed into the result, and the output shows seconds too, so precise timing works exactly the way you'd expect.