Convert Days to Seconds
Convert Days (d) to Seconds (s) instantly and accurately.
Conversion Formula
s = d × 86400
About Days
A day (d) = exactly 86,400 s. Earth's actual solar day varies ±16 s due to orbital eccentricity and axial tilt (equation of time). Leap seconds (abandoned in UTC after 2035) corrected the TAI-UT1 divergence. Mars's sol = 24 h 39 min 35 s ≈ 88,775 s; a Martian year = 668.6 sols. The day structures circadian biology, tides, and planetary science. 1 day = 86,400 s = 24 h.
About Seconds
The second (s) is the SI base unit of time, defined since 1967 as exactly 9,192,631,770 periods of the caesium-133 ground-state hyperfine transition at 0 K. Caesium fountain clocks realise this to ~10⁻¹⁶ (1 s lost per ~300 million years); optical lattice clocks (Sr, Yb) reach ~10⁻¹⁸. The second links to the metre via the defined speed of light c = 299,792,458 m/s exactly. 1 s = 1,000 ms = 1/60 min.
Quick Reference Table
| Days (d) | Seconds (s) |
|---|---|
| 1 d | 86400 s |
| 2 d | 172800 s |
| 5 d | 432000 s |
| 10 d | 864000 s |
| 25 d | 2160000 s |
| 50 d | 4320000 s |
| 100 d | 8640000 s |