Time Calculator
Add, subtract, and convert time durations
Duration
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Frequently Asked Questions
How do I add hours and minutes?
Add hours together, then minutes. If minutes exceed 60, carry over to hours. Example: 2h 45m + 1h 30m = 3h 75m = 4h 15m (carry 60 minutes = 1 hour). For larger durations, convert to total seconds first, then convert back to hours/minutes/seconds.
How do I calculate elapsed time?
Subtract start time from end time. If end < start, add 24 hours (for same-day crossing midnight). Example: 9:45 AM to 2:30 PM = 4 hours 45 minutes. In seconds: end - start = 14h30m - 9h45m = 4h45m = 17,100 seconds. Convert between units freely.
How many seconds are in a day, week, year?
60 seconds = 1 minute. 3,600 seconds = 1 hour. 86,400 seconds = 1 day. 604,800 seconds = 1 week. 31,536,000 seconds = 1 year (365 days). 31,557,600 seconds = 1 Julian year (365.25 days). Programmers often remember 86400 s/day and 3.15 × 10^7 s/year.
How do I convert decimal hours to hours and minutes?
0.5 hours = 30 minutes. 0.75 hours = 45 minutes. 2.25 hours = 2 hours 15 minutes. Formula: hours = floor(decimal). minutes = round((decimal - floor(decimal)) × 60). Example: 3.833 hours = 3 hours + (0.833 × 60) = 3 hours 50 minutes.
How do time zones work?
The Earth is divided into 24 standard time zones, each generally 15 degrees of longitude wide. UTC (Coordinated Universal Time) is the reference. US time zones: Eastern = UTC-5 (winter), UTC-4 (summer); Central = UTC-6/-5; Mountain = UTC-7/-6; Pacific = UTC-8/-7. Daylight Saving Time (DST) shifts clocks forward 1 hour in spring and back in fall (not all regions observe DST).