How to use the time calculator
- Pick what you want to do: Time ± duration moves a clock time forward or back, Duration ± duration combines two lengths of time, and Convert units changes one unit into another.
- For a clock time, enter the start date (optional) and start time. Leave the date blank if you only care about the time of day.
- For two durations, enter the first duration in days, hours, minutes and seconds.
- Choose Add or Subtract, then enter the days, hours, minutes and seconds to add or take away.
- To convert, enter the amount and pick the units to convert from and to.
How time is added
Everything is turned into seconds, added or subtracted, then turned back into days, hours, minutes and seconds:
The calculator uses clock time, where every day has exactly 24 hours. If the period crosses a daylight saving change, a real clock would jump an hour; to compare times in different places, use the time zone calculator. Average months and years come from the Gregorian calendar, which has 97 leap years in every 400, so the average year is 365.2425 days.
Worked example
The calculator opens with a start time of 9:00 AM today and adds 8 hours 30 minutes:
- 8 hours 30 minutes = 8 × 3,600 + 30 × 60 = 30,600 seconds.
- 9:00 AM plus 8 hours is 5:00 PM, and 30 more minutes gives 5:30 PM on the same day.
Subtracting 10 hours from 9:00 AM crosses midnight: the result is 11:00 PM the day before. In the duration mode, the defaults add 2 h 45 min to 8 h 30 min. The minutes make 75, which is 1 hour 15 minutes, so the total is 11 h 15 min. In the convert mode, 90 minutes ÷ 60 = 1.5 hours.
Minutes to decimal hours
Payroll systems and spreadsheets often want hours as a decimal instead of hours and minutes. Divide the minutes by 60:
| Minutes | Decimal hours | Minutes | Decimal hours |
|---|---|---|---|
| 5 | 0.083 | 35 | 0.583 |
| 10 | 0.167 | 40 | 0.667 |
| 15 | 0.25 | 45 | 0.75 |
| 20 | 0.333 | 50 | 0.833 |
| 25 | 0.417 | 55 | 0.917 |
| 30 | 0.5 | 60 | 1 |
So 7 hours 45 minutes is 7.75 hours, not 7.45. Mixing these up is the most common error when adding up time by hand. The hours calculator does this for a work shift, including breaks.
Common time questions
- Adding across midnight. 9:00 PM plus 1 day 5 hours 45 minutes is 2:45 AM two days later. Enter the date to see which day you land on.
- A million seconds is 11 days, 13 hours, 46 minutes and 40 seconds. Use the convert mode to check numbers like this.
- Subtracting a longer duration from a shorter one gives a negative result, shown with a minus sign, which tells you how far short the first one falls.
Frequently asked questions
How do I add hours and minutes together?
Add the minutes first. If they come to 60 or more, carry 1 hour for every 60 minutes, then add the hours. For 2 h 45 min plus 8 h 30 min: 45 + 30 = 75 minutes, which is 1 h 15 min, and 2 + 8 + 1 = 11 hours, so the total is 11 h 15 min.
What time will it be in 8 hours?
Add 8 to the current hour. If the result is 12 or more, it moves from AM to PM (or from PM to AM the next day). From 9:00 AM, 8 hours later is 5:00 PM; from 9:00 PM, it's 5:00 AM the next morning.
How many seconds are in a day, a week and a year?
A day has 86,400 seconds and a week has 604,800. A 365-day year has 31,536,000 seconds, and the average Gregorian year of 365.2425 days has 31,556,952. The convert mode shows any amount in all of these units at once.
Does the calculator handle daylight saving time?
No, on purpose: it adds clock hours, so 9:00 AM plus 24 hours is always 9:00 AM the next day. On the night clocks change, the real elapsed time between those two moments is 23 or 25 hours. For the length of time between two dates and times, use the time duration calculator.
Related calculators
- Time Duration Calculator — The exact time between two dates and times, in days, hours and minutes, with totals in every unit.
- Hours Calculator — Hours worked between a start and end time, minus an unpaid break, in hours and minutes and in decimal hours.
- Date Calculator — Add or subtract years, months, weeks and days from a date, or count the days and weekdays between two dates.
- Time Zone Calculator — Convert a date and time between world time zones, with daylight saving applied, and see the same moment in 40+ cities.
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