Time units mix base-60 (seconds/minutes), base-24 (hours), and base-365 (years) systems. Unlike metric conversions, time is not decimal-based.
The Structure of Time Units
1 minute = 60 seconds, 1 hour = 3,600 seconds, 1 day = 86,400 seconds. These are exact by definition. A week is exactly 7 days = 604,800 seconds.
Days, Weeks, and Years
A common year is 365 days; a leap year is 366 days. The average tropical year is 365.2422 days. For scientific work, the Julian year (365.25 days = 31,557,600 seconds) is standard.
Practical Conversions
1 million seconds ≈ 11.57 days. 1 billion seconds ≈ 31.7 years. A nanosecond is 10⁻⁹ seconds — light travels about 30 cm in one nanosecond.
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Frequently Asked Questions
How many seconds are in a day?
Exactly 86,400 seconds (24 × 60 × 60).
How many weeks are in a year?
A common year has 52.14 weeks (365 ÷ 7). On average, a year has about 52.18 weeks.