How this time calculator works
Add or subtract days, hours, minutes, and seconds. Each time value is converted to seconds using 1 day = 86,400 seconds, 1 hour = 3,600 seconds, and 1 minute = 60 seconds. The answer is converted back to days, hours, minutes, and seconds.
Add or subtract time from a date
Choose a start date and either an AM/PM time or a 24-hour clock time. Add or subtract a duration to find the resulting calendar date, weekday, and time. Use current time fills in your local clock when clicked. Calculations use fixed 24-hour days and do not model daylight saving transitions, time zones, or leap seconds.
Time calculator in expression
Enter multiple durations using d, h, m, and s with plus and minus signs, such as 1d 2h + 45m - 20s. A sign applies to the following group of units until the next sign. This is duration arithmetic, not multiplication or division.
Understanding the result
Values greater than their usual unit range are normalized: 90 minutes becomes 1 hour and 30 minutes. A negative duration puts a minus sign on each nonzero result component. Blank duration fields count as zero. Fractional units are accepted; duration seconds are displayed to six decimal places.
Frequently asked questions
How do I add hours and minutes?
Enter the first and second time values and select Add. For example, 1 hour 45 minutes plus 30 minutes is 2 hours 15 minutes.
Can a time subtraction result be negative?
Yes. Subtracting 2 hours from 1 hour 30 minutes gives −30 minutes.
What happens when I cross midnight?
In date mode, the result moves to the previous or next calendar date as needed. Month boundaries and leap years are handled automatically.
Is 12 AM noon or midnight?
12 AM is midnight; 12 PM is noon. Choose AM or PM before calculating a date and time.
What's changed
- Launched with Add / subtract time, Time from a date, and Time expression tabs.
References
- NIST Guide to the SI, Table 6
defines the minute, hour, and day conversions used in this calculator