How time is added
Time doesn't use base 10, so you can't add 1:45 and 2:30 like decimals. The calculator turns everything into seconds, adds or subtracts, then splits the answer back up:
Seconds = days × 86,400 + hours × 3,600 + minutes × 60 + seconds
Then: days = ⌊total ÷ 86,400⌋, hours = ⌊rest ÷ 3,600⌋, minutes = ⌊rest ÷ 60⌋, seconds = what's left
Then: days = ⌊total ÷ 86,400⌋, hours = ⌊rest ÷ 3,600⌋, minutes = ⌊rest ÷ 60⌋, seconds = what's left
Worked example
1 day 2 hours 30 minutes + 22 hours 45 minutes 15 seconds:
- First: 86,400 + 7,200 + 1,800 = 95,400 seconds.
- Second: 79,200 + 2,700 + 15 = 81,915 seconds.
- Sum: 177,315 seconds = 2 days (172,800) + 1 hour (3,600) + 15 minutes (900) + 15 seconds = 2 days, 1 hour, 15 minutes, 15 seconds.
Units used
| Unit | In seconds |
|---|---|
| 1 minute | 60 |
| 1 hour | 3,600 |
| 1 day | 86,400 |
| 1 week | 604,800 |
Limitations
- Months and years aren't offered, because they have different lengths (28 to 31 days, 365 or 366 days). Use the date calculator to add months or years to a date.
- A "day" here is exactly 24 hours. A calendar day with a daylight saving change is 23 or 25 hours, and very rarely a minute has a leap second.
- For the time between two clock times, like 9:15 AM to 5:40 PM, the hours calculator is quicker.
Sources
- BIPM: the SI second (the definition all time units build on)