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Time Calculator

Add or subtract hours, minutes, and seconds. Find the time difference between two clock times. Convert between time units. Results show step-by-step working.

A. Add or Subtract Time

Result: 10:30:00(10 hours 30 minutes 0 seconds)
Start time = 09:00:00 (32400 seconds) + Duration = 01:30:00 (5400 seconds) ───────────────── Result = 10:30:00 In hours/min/sec = 10 hours 30 minutes 0 seconds

B. Time Between Two Times

Duration: 8 hours 30 minutes 0 seconds= 8.50 hours = 510 minutes
End time = 17:30:00 (63000 seconds) Start time = 09:00:00 (32400 seconds) Difference = 63000 − 32400 = 30600 seconds = 8 hours 30 minutes 0 seconds = 8.5000 hours = 510.00 minutes = 30600 seconds

C. Convert Time Units

Days0.354167
Hours8.5
Minutes510
Seconds30,600
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How to Add Time

Adding time works like standard addition but with carries that happen at 60 (seconds to minutes) and 60 (minutes to hours), not at 10 like in decimal arithmetic. The procedure is:

Step 1 — Add seconds. Sum the seconds from all values. If the total is 60 or more, divide by 60: the quotient carries forward as extra minutes, the remainder stays as seconds.

Step 2 — Add minutes. Sum the minutes plus any carry from step 1. If the total is 60 or more, divide by 60: the quotient carries forward as extra hours, the remainder stays as minutes.

Step 3 — Add hours. Sum the hours plus any carry from step 2.

Example: 2h 45m 30s + 1h 35m 45s Step 1 — Seconds: 30 + 45 = 75s → 75 ÷ 60 = 1 carry, 15s remain Step 2 — Minutes: 45 + 35 + 1 (carry) = 81m → 81 ÷ 60 = 1 carry, 21m remain Step 3 — Hours: 2 + 1 + 1 (carry) = 4h Result: 4 hours, 21 minutes, 15 seconds

How to Subtract Time

Subtracting time requires borrowing when the smaller value's component exceeds the larger value's component, just like multi-digit subtraction — but borrowing happens in units of 60.

Example: 3h 15m 10s − 1h 45m 40s Step 1 — Seconds: 10 − 40 is negative, so borrow 1 minute (60 seconds). 10 + 60 = 70s − 40s = 30s remain Minutes remaining: 15 − 1 (borrowed) = 14m Step 2 — Minutes: 14 − 45 is negative, so borrow 1 hour (60 minutes). 14 + 60 = 74m − 45m = 29m remain Hours remaining: 3 − 1 (borrowed) = 2h Step 3 — Hours: 2h − 1h = 1h Result: 1 hour, 29 minutes, 30 seconds

When calculating the time between two clock times (e.g., 8:45 AM to 5:30 PM), it is often easier to convert both times to total minutes from midnight, subtract, then convert back:

8:45 AM = 8 × 60 + 45 = 525 minutes from midnight 5:30 PM = 17 × 60 + 30 = 1050 minutes from midnight Difference = 1050 − 525 = 525 minutes 525 ÷ 60 = 8 hours remainder 45 minutes Time between = 8 hours 45 minutes

Time Unit Conversions

Unit Equals
1 minute60 seconds
1 hour60 minutes = 3,600 seconds
1 day24 hours = 1,440 minutes = 86,400 seconds
1 week7 days = 168 hours = 10,080 minutes
1 month (avg)30.4375 days = 730.5 hours (calendar average)
1 year (Julian)365.25 days = 8,766 hours = 525,960 minutes
1 decade10 years (3,652 or 3,653 days including leap years)
1 fortnight14 days = 2 weeks = 336 hours
1 quarter91–92 days (13 weeks)
1 millisecond0.001 seconds = 10−3 s
1 microsecond0.000001 seconds = 10−6 s
1 nanosecond10−9 seconds

Note: A calendar month varies from 28 to 31 days. The average of 30.4375 days (365.25 ÷ 12) is used when precision is needed and the specific month does not matter. For financial calculations (mortgages, loan interest), months are often treated as exactly 1/12 of a year.

Frequently Asked Questions

How do time zones affect time calculations?

Time zone differences can cause confusion when adding or subtracting times across zones. The safest approach is to convert both times to UTC (Coordinated Universal Time) first, perform the calculation in UTC, then convert back to the desired local time. For example, a meeting at 3:00 PM EST (UTC−5 = 20:00 UTC) and another at 9:00 AM PST (UTC−8 = 17:00 UTC) are 3 hours apart. Always specify time zones when scheduling across regions, and use ISO 8601 format (2026-04-12T15:00:00-05:00) for unambiguous timestamps in technical contexts.

What is the difference between 12-hour and 24-hour time?

The 12-hour clock repeats AM and PM cycles, each running from 12 (midnight or noon) through 11:59. Midnight is 12:00 AM, noon is 12:00 PM, and 1:00 PM corresponds to 13:00 in 24-hour (military) time. The 24-hour clock runs from 00:00 (midnight) to 23:59 and is unambiguous — there is only one 13:00, whereas "1:00" requires AM/PM qualification in the 12-hour system. Converting 12-hour to 24-hour: add 12 to PM hours (except 12:xx PM stays as 12:xx), set 12:xx AM to 00:xx.

How do I calculate elapsed time for work or timesheets?

To find hours worked between a start and end time, subtract the start from the end, then subtract any unpaid breaks. Convert the result to decimal hours if your payroll system requires it. For example: Start 8:45 AM, End 5:30 PM, Lunch break 45 minutes. Elapsed = 5:30 PM − 8:45 AM = 8 hours 45 minutes. Minus 45-minute break = 8 hours 0 minutes = 8.0 hours. If you clocked 6 hours 20 minutes, that is 6 + (20/60) = 6.333 hours for a timesheet that uses decimal notation.

When does overtime begin and how is it calculated?

In the United States, the Fair Labor Standards Act (FLSA) requires overtime pay at 1.5× the regular rate for all hours worked beyond 40 in a workweek for non-exempt employees. Some states have daily overtime thresholds — California requires daily overtime after 8 hours and double time after 12 hours. Canada, the UK, and EU countries have their own overtime rules, which vary by province, country, and employment contract. Always check the applicable labor law and your employment contract. To calculate overtime pay: (regular rate × 40 hours) + (regular rate × 1.5 × overtime hours).

What is military time and how do I convert it?

Military time (also called the 24-hour clock) expresses time as a 4-digit number from 0000 to 2359, with no AM/PM. The first two digits are hours (00–23) and the last two are minutes. To convert military time to standard: hours 01–12 are AM; hours 13–23 subtract 12 to get PM hours; 0000 = 12:00 AM midnight; 1200 = 12:00 PM noon. Examples: 0830 = 8:30 AM, 1430 = 2:30 PM, 2215 = 10:15 PM. Military time eliminates the ambiguity of the 12-hour system and is used in aviation, healthcare, military operations, and international scheduling.

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