Skip to content
CalculatorBuddy

Time Calculator

Add or subtract time in days, hours, minutes, and seconds — between two time values, from a starting date and time, or from a free-text time expression.

Operation

Result

0 seconds

In hours
0 hours
In minutes
0 minutes
In seconds
0 seconds
Result0 secondsView results

Add and subtract time three ways: combine two day/hour/minute/second values, apply a span to a starting date and time, or evaluate a free-form time expression. Every result is normalized to days, hours, minutes, and seconds (and shown in total hours, minutes, and seconds).

Formula

All modes convert each value to seconds, apply the operations, then normalize back:

total seconds = days×86,400 + hours×3,600 + minutes×60 + seconds
days = ⌊total ÷ 86,400⌋   hours = ⌊remainder ÷ 3,600⌋
minutes = ⌊remainder ÷ 60⌋   seconds = remainder

For a date, the start date and time of day become seconds since a reference day; adding the span and converting back gives the new date and clock time.

In the expression tab, an operator applies to the whole value group that follows it: "1d 2h - 30m" adds a day and two hours, then subtracts 30 minutes.

Time units

UnitSeconds
1 minute60
1 hour3,600
1 day86,400
1 week604,800

Examples

Add two times

2 days 5 hours 30 minutes plus 1 day 20 hours 45 minutes equals 4 days, 2 hours, 15 minutes (353,700 seconds).

Evaluate an expression

"1d 2h 3m 4s + 4h 5s - 2030s + 28h" totals 206,959 seconds, which is 2 days, 9 hours, 29 minutes, 19 seconds.

Add time to a date

Starting at 12:00:00 on June 17, 2026 and adding 30 hours gives 18:00:00 on Thursday, June 18, 2026.

Frequently asked questions

How do I add two times together?
In the "Add / Subtract Time" tab, enter each time as days, hours, minutes, and seconds, choose add or subtract, and the calculator returns the combined time normalized to days, hours, minutes, and seconds — for example 2h 45m + 1h 30m = 4 hours, 15 minutes.
What happens if subtracting gives a negative time?
The result is shown with a minus sign. Subtracting a larger time from a smaller one yields a negative span, such as 1h − 90m = −30 minutes.
How does adding time to a date work?
In the "Add / Subtract to a Date" tab, enter a start date and a time of day (24-hour), then the days, hours, minutes, and seconds to add or subtract. The calculator rolls the time over across midnight and returns the resulting date, time, and day of the week.
What is the time expression format?
The "Time Expression" tab evaluates a string using d, h, m, and s with + and − operators, like "1d 2h 3m 4s + 4h 5s - 2030s + 28h". Each value group is summed according to the operator before it.
How many seconds are in a day, hour, and minute?
A day is 86,400 seconds, an hour is 3,600 seconds, and a minute is 60 seconds. All time arithmetic here is done by converting to seconds and back.

Related calculators