Time Calculator
Add or subtract time durations and convert between time zones worldwide.
- Free forever
- Instant results
- Private — runs in your browser
Time result
How to use the Time calculator
Add / subtract durations: enter two lengths of time in hours, minutes and seconds and choose + or −. Values can overflow (e.g. 90 minutes) and are normalised automatically.
Time zone converter: pick a date and time, the zone it is in, and the zone you want — the result accounts for daylight-saving time on that specific date.
Formula
Durations are converted to seconds: total = h × 3600 + m × 60 + s, added or subtracted, then converted back to h/m/s.
Time zones use your browser’s built-in IANA time-zone database, so DST rules are applied for the exact date you enter.
Frequently asked questions
Can I subtract more time than the first value?
Yes — the result is shown as a negative duration.
Does the time zone converter handle daylight saving time?
Yes. Offsets are looked up for the exact date and time you enter, so converting a summer date and a winter date between the same cities can give different results.
What happens with a time that does not exist because clocks spring forward?
Times inside a daylight-saving gap (for example 2:30 am on the night clocks jump to 3:00) do not exist locally. The converter treats them as the matching standard-time reading, so the result is shifted by the size of the DST jump (usually one hour). Pick a time outside the gap for an exact answer.