Time Calculator

Add and subtract time durations in days, hours, minutes, and seconds. Convert between time units and handle carry-over arithmetic automatically.

Time Arithmetic Mode

Sexagesimal
Quick Presets
Duration 1 (Days, Hours, Minutes, Seconds)
days
hrs
min
sec
+
Duration 2 (Days, Hours, Minutes, Seconds)
days
hrs
min
sec
Result Duration
4 hours, 15 minutes
4.25 Decimal Hours

Total Seconds

15,300 s

Total Minutes

255.00 min

Total Hours

4.25 hrs

Total Days

0.177 days

Comprehensive Unit Breakdown

Weeks0.025
8-Hour Workdays0.53
Milliseconds15,300,000
Year % (365d)0.05%

Sexagesimal Carry-Over Math

Unlike decimal math where 100 hundredths make a whole, 60 seconds roll over to 1 minute, 60 minutes roll over to 1 hour, and 24 hours roll over to 1 day.

Sexagesimal Time Math & Carry-Over Arithmetic

Standard arithmetic uses base-10 decimal notation, but time measurement uses the ancient Babylonian base-60 (sexagesimal) system for minutes and seconds, combined with base-24 for solar days. When adding minutes or seconds that exceed 60, the excess must be converted into whole higher units.

1. Universal Total Seconds Conversion Formula
Total Seconds (S)=(Days × 86,400)+(Hours × 3,600)+(Minutes × 60)+Seconds
2. Sexagesimal Modulo Decomposition Equation
Days = ⌊ Total Sec ÷ 86,400 ⌋Hours = ⌊ (Total Sec mod 86,400) ÷ 3,600 ⌋
•
Minutes = ⌊ (Total Sec mod 3,600) ÷ 60 ⌋Seconds = Total Sec mod 60
Step-by-Step Calculation Breakdown
Step 1: Add Time Durations (2h 45m + 1h 30m)
Minutes Sum = 45 min + 30 min = 75 Minutes
Convert Minutes: 75 ÷ 60 = 1 hour and 15 minutes remainder (carry 1 hour)
Step 2: Sum Whole Hours & Carried Units
Hours Sum = 2 hours + 1 hour + 1 carried hour = 4 Hours
Combined Duration = 4 hours, 15 minutes, 0 seconds
Step 3: Verification in Decimal Format
Equivalent Decimal=4 + (15 ÷ 60)=4.25 Decimal Hours (15,300 Seconds)

Time Unit Conversion Reference Table

Time UnitIn SecondsIn MinutesIn HoursIn Days
1 Minute60 s1.0 min0.0167 hr0.00069 days
1 Hour3,600 s60 min1.0 hr0.0417 days
1 Day86,400 s1,440 min24.0 hr1.0 day
1 Week (7 Days)604,800 s10,080 min168.0 hr7.0 days

Frequently Asked Questions

How do I add hours and minutes together?
Enter the days, hours, minutes, and seconds for each duration, then select 'Add Times'. The calculator automatically handles base-60 sexagesimal carry-overs. For example, 1 hour 45 minutes + 30 minutes becomes 2 hours 15 minutes because 75 minutes equals 1 hour and 15 minutes.
Can I add times with different units?
Yes! You can mix days, hours, minutes, and seconds in any combination. The calculator converts all inputs to standard SI seconds internally, executes the arithmetic, and decomposes the result back into cleanly formatted days, hours, minutes, and seconds.
What happens when I subtract a larger time duration from a smaller duration?
The calculator displays a negative time result. For example, subtracting 2 hours from 1 hour yields −1 hour (−60 minutes / −3,600 seconds). This is helpful for calculating time deficits or tracking flex-time balances.
How many seconds are in a day, week, and year?
There are exactly 86,400 seconds in a standard day (24 hours × 60 minutes × 60 seconds). A 7-day week contains 604,800 seconds (168 hours), and a standard 365-day calendar year contains 31,536,000 seconds (8,760 hours).
How do I convert seconds into hours, minutes, and seconds?
To convert seconds: divide total seconds by 3,600 to find whole hours, take the remaining seconds and divide by 60 to find whole minutes, and the remaining remainder is the seconds. For example, 5,000 seconds = 1 hour, 23 minutes, and 20 seconds.

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