Dates and time
Time Calculator
Add and subtract hours, minutes, and seconds, find the time between two clock times, work out what time it will be after a span, and multiply or divide a time.
Maintained by Austin Witherow · Updated
Result
8 hours
- Hours:minutes
- 8:00
- Decimal hours
- 8 hours
- Total minutes
- 480 minutes
- From and to
- 9:00 a.m. → 5:00 p.m., same day
Formula
Time between = End − Start (plus 24 hours if the end is earlier)Adding: 1:30 + 0:45 = 1 h 75 min = 2:15 (each 60 minutes carry to an hour)Decimal hours = Hours + Minutes ÷ 60
Key caveat
Without dates, an end time earlier than the start counts as the next day, so 10 p.m. to 6 a.m. is 8 hours. Add dates for spans longer than a day.
What this calculator is for
Time does not add like ordinary numbers: 60 minutes make an hour and 24 hours make a day, so 2:45 plus 1:30 is 4:15, not 3:75. This calculator does the carrying for you. Add or subtract a list of times, find the hours and minutes between two clock times or dates, see what time it will be after a span, or multiply and divide a time.
Spans also come as decimal hours, total minutes, and total seconds, for timesheets and invoices. An end time earlier than the start counts as the next day, so overnight shifts work without extra steps. With dates, the result also checks for a U.S. daylight saving change.
How it works
Each time is turned into seconds: hours × 3,600, plus minutes × 60, plus seconds. 1:30 means 1 hour 30 minutes; 1:30:15 adds 15 seconds.
Times are added or subtracted as seconds, then turned back into hours, minutes, and seconds. That does the carrying: every 60 minutes becomes an hour.
Time between two times is the end minus the start. Without dates, an earlier end is taken as the next day; with dates, the span can run for days.
A clock time plus a span steps forward on the calendar as needed, so 11:30 p.m. plus 2 hours 45 minutes is 2:15 a.m. the next day.
Decimal hours are total minutes ÷ 60, to two decimals.
Results count the clock as written, with every day 24 hours long. When dates are given and the span crosses a U.S. daylight saving change, the result says so and gives the elapsed-time answer too.
That check converts both ends to standard time, using the U.S. dates in 15 U.S.C. 260a since 1987. A time in the hour repeated in fall or skipped in spring is flagged.
How times add and wrap past midnight
Top: 2:45 plus 1:30. The minutes come to 75, which is 1 hour and 15 minutes, so the hour carries and the total is 4:15. Bottom: a shift from 10:15 p.m. to 6:45 a.m. on a 24-hour line. It runs 1 hour 45 minutes to midnight and 6 hours 45 minutes after, 8 hours 30 minutes in all.
Quick calculator insights
Where time math goes wrong
- Adding like decimals
- 2:45 + 1:30 is 4:15, not 3:75 or 4.15. Carry each 60 minutes into an hour.
- 1:30 is not 1.3 hours
- 1 hour 30 minutes is 1.5 decimal hours. Divide the minutes by 60.
- Overnight spans
- 10 p.m. to 6 a.m. is 8 hours. Subtracting 22 from 6 gives −16; add 24.
- Clock changes
- A span across a daylight saving change ends an hour off on the clock.
Minutes as decimal hours
Minutes ÷ 60, rounded to two decimals.
| Minutes | Decimal hours |
|---|---|
| 6 | 0.10 |
| 10 | 0.17 |
| 15 | 0.25 |
| 20 | 0.33 |
| 30 | 0.50 |
| 40 | 0.67 |
| 45 | 0.75 |
| 50 | 0.83 |
12-hour and 24-hour clock
NIST: say noon and midnight, not 12 p.m. and 12 a.m.
| 24-hour | 12-hour |
|---|---|
| 00:00 | Midnight, start of the day |
| 06:30 | 6:30 a.m. |
| 12:00 | Noon |
| 12:30 | 12:30 p.m. |
| 13:45 | 1:45 p.m. |
| 18:00 | 6:00 p.m. |
| 23:59 | 11:59 p.m. |
| 24:00 | Midnight, end of the day |
How to use this calculator
- 01Choose a tab: Time between, Add / subtract, Hours from now, or Multiply / divide.
- 02Enter hours and minutes for each time, adding a row per time, or set the start and end times.
- 03Read the result in hours and minutes, decimal hours, and total minutes.
- 04For a clock time, check the day and the daylight saving line.
Inputs explained
- Calculate
- Add or subtract a list of times; the time between two clock times; a clock time plus or minus a span; or one time multiplied or divided.
- Times
- One row per time, with hours and minutes boxes; pick − at the start of a row to subtract it. Minutes over 59 carry over. Or choose Type or paste a list and use h:mm (1:30), h:mm:ss (1:30:15), or units (2h 15m, 90 min, 1.5h, 1d 4h), one per line.
- Start time and end time
- Clock times for Time between. Type the hour and minute and set AM or PM, or tap Now. The start begins as the time now, for the time until something.
- Add dates
- Tap Add dates to pick a start and end date, for spans over a day and the daylight saving check. Without dates, an earlier end time counts as the next day.
- Start date and start time
- For Hours from now. They start as today and the time now on your device.
- Amount of time
- The span to add or subtract, in hours and minutes; +15m, +30m, +1h, and +8h add to it. For days, use hours: 3 days is 72 hours.
- Time, operation, and number
- For Multiply / divide: a time and the number to multiply or divide it by.
Outputs explained
- Result
- The answer in words: a span in hours and minutes, or a date and clock time.
- In days, hours, and minutes
- Spans of a day or more split into days; shorter spans say less than a day.
- Hours:minutes
- The span as h:mm, or h:mm:ss with seconds. Hours keep counting past 24, as on a timesheet.
- Decimal hours, total minutes, total seconds
- The same span as one number, for payroll or billing systems.
- Running total
- The total after each time in the list, to check the entries.
- From and to
- For Time between: the start and end in 12-hour time, with dates or whether the end falls the next day.
- 24-hour clock and day
- For Hours from now: the result on a 24-hour clock, and how many days later or earlier it falls.
- Daylight saving
- For a clock time, or Time between with dates: whether the span crosses a U.S. clock change, and the elapsed-time answer where clocks change. Years before 1987 are not checked.
Worked examples
Add a week of shifts
- Shifts: 7:45, 8:20, 6:55, 8:10, and 7:30.
- Minutes: 45 + 20 + 55 + 10 + 30 = 160, which is 2 hours 40 minutes. Hours: 7 + 8 + 6 + 8 + 7 = 36, plus the 2 carried = 38.
- Total: 38 hours 40 minutes, or 38.67 decimal hours (2,320 minutes ÷ 60).
Overnight: 10:15 p.m. to 6:45 a.m.
- The end is earlier than the start, so it is the next morning.
- 10:15 p.m. to midnight is 1 hour 45 minutes; midnight to 6:45 a.m. is 6 hours 45 minutes.
- Total: 8 hours 30 minutes, or 8.5 decimal hours.
What time will it be 2 hours 45 minutes after 11:30 p.m.?
- Starting Friday, October 9, 2026 at 11:30 p.m.: 30 minutes takes it to midnight.
- The other 2 hours 15 minutes run into the next day: 2:15 a.m. on Saturday, October 10, 2026.
Across the fall clock change
- Start: Saturday, October 31, 2026 at 10:00 p.m. Add 8 hours.
- By the clock as written: 6:00 a.m. on Sunday, November 1.
- U.S. clocks go back an hour at 2 a.m. that morning, so 8 hours of elapsed time ends at 5:00 a.m. on the clock where the change applies.
Divide a time into equal parts
- 7 hours 30 minutes is 450 minutes. Divided by 4: 112.5 minutes.
- That is 1 hour 52 minutes 30 seconds each, or 1:52:30.
When to use it
- Adding up hours worked across a week.
- Finding the length of a shift, a flight, or a drive, including overnight.
- Working out what time it will be after a few hours.
- Totaling race splits, video clips, or practice sessions.
- Splitting a block of time into equal parts.
Tips
- For hours until a time, choose Time between: the start is already the time now.
- In a typed list, times with seconds need both colons: 0:01:30 is 1 minute 30 seconds, while 1:30 is 1 hour 30 minutes.
- If a timesheet asks for decimal hours, use that line, not hours:minutes.
- To find what time something started, choose Hours from now and Earlier (−).
Limitations
- Without dates, an end time earlier than the start counts as the next day, so 10 p.m. to 6 a.m. is 8 hours. Add dates for spans longer than a day.
- In a typed list, 1:30 is read as hours and minutes; for minutes and seconds, write 0:01:30 or 1m 30s.
- Clock times are to the minute; spans can include seconds with Add seconds.
- Daylight saving checks use the U.S. dates since 1987 and do not know your time zone or state. Time between without dates does not check.
- Every day counts as 86,400 seconds on the clock; clock changes are flagged, and leap seconds are ignored.
- Decimal results are rounded to two places; seconds are rounded to the nearest whole second.
Methodology & assumptions
- Units follow NIST SP 811: a minute is 60 seconds, an hour 3,600, and a day 86,400.
- Noon and midnight are written as NIST advises, not as 12 p.m. or 12 a.m.
- Daylight saving dates follow 15 U.S.C. 260a and its 1986 and 2005 amendments.
- Times are added as whole seconds, so there is no rounding until the decimal display.
Sources
Last reviewed 2026-10-08
- NIST SP 811, Chapter 5: Units Outside the SI
Table 6: 1 min = 60 s; 1 h = 60 min = 3,600 s; 1 d = 24 h = 86,400 s.
- NIST: Times of Day FAQs
12 a.m. and 12 p.m. are ambiguous and should not be used; say noon or midnight. On a 24-hour clock, 0000 is midnight at the start of a day and 2400 midnight at its end.
- 15 U.S. Code § 260a: Advancement of time or changeover dates (Cornell LII)
Standard time advances one hour from 2 a.m. on the second Sunday of March to 2 a.m. on the first Sunday of November, from 2007. The 1986 amendment set the first Sunday of April, and the end was the last Sunday of October until 2007. A state may exempt itself by observing standard time all year.
- NIST: Leap Seconds FAQs
Leap seconds are added to UTC, at the end of June or December, to keep it within 0.9 seconds of time based on Earth's rotation, which the IERS measures; the clock reads 23:59:60 before 00:00:00.
FAQs
How do you add time?+
Add the minutes, then the hours. Every 60 minutes carries 1 hour. 2:45 + 1:30: 45 + 30 = 75 minutes, which is 1 hour 15 minutes; 2 + 1 + 1 = 4 hours. Total: 4:15.
How do I add 30 or 45 minutes to a time?+
Add the minutes, and if they pass 60, take off 60 and add an hour. 9:40 plus 30 minutes is 10:10; 9:40 plus 45 minutes is 10:25. Use Hours from now to do it for any start time.
How do you subtract time?+
Subtract the minutes, then the hours. If the minutes come up short, borrow an hour as 60 minutes. 5:10 − 2:35: borrow, so 70 − 35 = 35 minutes and 4 − 2 = 2 hours. Result: 2:35.
How many hours are there between two times?+
The end time minus the start time. 8:30 a.m. to 5:15 p.m. is 8 hours 45 minutes, or 8.75 decimal hours. Choose Time between and enter both times.
How do I count hours across midnight?+
Add 24 hours to the end time, or count to midnight and then from it. 10:15 p.m. to 6:45 a.m. is 1 hour 45 minutes plus 6 hours 45 minutes: 8 hours 30 minutes. This calculator does it when the end is earlier than the start.
How many hours until 9?+
Choose Time between, tap Now for the start, and set the end to 9:00 a.m. or 9:00 p.m. From 2:20 p.m. to 9:00 p.m. is 6 hours 40 minutes. If 9:00 has passed today, it counts to 9:00 tomorrow.
What time will it be in 8 hours?+
Add 8 to the hour. If that passes 12, subtract 12 and switch a.m. and p.m.; going from p.m. to a.m. means the next day. 7:15 p.m. plus 8 hours is 3:15 a.m. tomorrow. Hours from now starts at the time now and shows the date.
How do I convert minutes to decimal hours?+
Divide the minutes by 60. 15 minutes is 0.25 hours, 30 is 0.5, 45 is 0.75, and 20 is 0.33. So 7 hours 45 minutes is 7.75 hours.
How do I turn decimal hours into hours and minutes?+
Keep the whole hours and multiply the decimal part by 60. 7.8 hours is 7 hours plus 0.8 × 60 = 48 minutes: 7 hours 48 minutes.
Is 12 p.m. noon or midnight?+
Clocks show noon as 12:00 p.m., but NIST calls 12 a.m. and 12 p.m. ambiguous, since noon is neither before nor after noon. Write noon or midnight instead, or use a 24-hour clock, where noon is 12:00.
Is midnight the start or the end of a day?+
Both, which is why NIST suggests 11:59 p.m. or 12:01 a.m. on legal documents. On a 24-hour clock, 00:00 is midnight at the start of a date and 24:00 at its end.
What is military time?+
The 24-hour clock: hours run 00 to 23, so 1:45 p.m. is 13:45 and 6:00 p.m. is 18:00. From 1:00 p.m. to 11:59 p.m., add 12 to the hour. 12:30 p.m. stays 12:30, and 12:30 a.m. is 00:30.
How does daylight saving time change the answer?+
U.S. clocks go forward an hour at 2 a.m. on the second Sunday of March and back at 2 a.m. on the first Sunday of November (15 U.S.C. 260a). A span across a change is an hour off on the clock. With dates, this calculator flags it and gives both answers; states that skip daylight saving have no change.
How do I multiply or divide a time?+
Turn it into minutes, multiply or divide, and turn it back. 1:15 × 4 = 75 × 4 = 300 minutes = 5 hours. 7:30 ÷ 4 = 450 ÷ 4 = 112.5 minutes = 1 hour 52 minutes 30 seconds.
How many 25-minute blocks fit in 3 hours?+
Divide in the same unit: 180 minutes ÷ 25 = 7.2, so 7 whole blocks with 5 minutes left. Use total minutes from this calculator for both times, then divide.
How do I enter seconds?+
Choose Add seconds under the boxes for a seconds box. In a typed list, use hours:minutes:seconds, like 0:04:35 for 4 minutes 35 seconds, or units, like 4m 35s; 1:30 alone means 1 hour 30 minutes. Weeks work in a typed list too: 2w 3d.
Does every day have 86,400 seconds?+
No. Where clocks change, the spring day has 23 hours and the fall day 25. And now and then a leap second is added to UTC, at the end of June or December, to keep it in step with Earth's rotation. This calculator flags clock changes when it has dates and ignores leap seconds.
Related calculators
This calculator does time arithmetic. It does not apply payroll rounding or overtime rules; check those with your employer or the rule that applies.