Convert Months to Sidereal Years
Convert Months (mo) to Sidereal Years (a_sid) instantly and accurately.
Conversion Formula
a_sid = mo × 0.08333017049
About Months
A mean Gregorian calendar month = 365.2425 ÷ 12 = 30.436875 days = 2,629,746 s exactly (averaged over the 400-year cycle with exactly 97 leap years). Individual months have 28-31 days. Loan schedules, subscriptions, and mobile billing reference 'per month', requiring explicit agreement on meaning. ISO 8601 uses 'P1M'. 1 mo = 30.436875 d = 2,629,746 s.
About Sidereal Years
The sidereal year = Earth's orbital period relative to the stars = 365.25636 days = 31,558,149.8 s - about 20 min 24 s longer than the tropical year. The gap arises from precession of the equinoxes (~50 arcsec/year westward drift), which causes the tropical year to end slightly before the sidereal orbit completes. JPL DE440 ephemerides and J2000.0 epoch are anchored to the sidereal frame. 1 a_sid = 365.25636 d.
Quick Reference Table
| Months (mo) | Sidereal Years (a_sid) |
|---|---|
| 1 mo | 0.0833302 a_sid |
| 2 mo | 0.16666 a_sid |
| 5 mo | 0.416651 a_sid |
| 10 mo | 0.833302 a_sid |
| 25 mo | 2.08325 a_sid |
| 50 mo | 4.16651 a_sid |
| 100 mo | 8.33302 a_sid |