1 day = 86,400 seconds
A day has 24 hours, each hour has 60 minutes and each minute has 60 seconds. Multiply them: 24 × 60 × 60 = 86,400. Every ordinary day has exactly this many seconds; the only exceptions are the rare leap-second days, which have 86,401.
| Unit | Amount | Working |
|---|---|---|
| 1 hour | 3,600 | 60 × 60 |
| 1 day | 86,400 | 24 × 3,600 |
| 1 week | 604,800 | 7 × 86,400 |
| 30 days | 2,592,000 | 30 × 86,400 |
| 1 year (365 d) | 31,536,000 | 365 × 86,400 |
| 1 leap year | 31,622,400 | 366 × 86,400 |
How many seconds in half a day?
43,200. Twelve hours × 3,600 seconds.
How many seconds in a week?
604,800. Seven days × 86,400.
How many seconds in a year?
31,536,000 in a normal year and 31,622,400 in a leap year. The average, allowing for leap years, is 31,557,600.
How many seconds in a month?
Between 2,419,200 (28 days) and 2,678,400 (31 days). A 30-day month has 2,592,000 seconds.
Why 365.25?
Converters use 365.25 days per year (the four-year leap-year average). The calendar’s long-run average is 365.2425, a difference of about 11 minutes a year, so treat year and month figures as close approximations.
Why 60 and 24?
The Babylonians counted in 60s, which divides neatly by 2, 3, 4, 5, 6, 10, 12, 15, 20 and 30. The 24-hour day comes from the Egyptians, who split day and night into 12 hours each.