Convert Years to Seconds

The Year (symbol: yr) is a unit of time. A unit of time corresponding to Earth's orbital period around the Sun, with several formal definitions depending on context: the Julian year used for unit conversions is exactly 365.25 days = 31,557,600 seconds per IAU 1976 definition; the tropical year (equinox to equinox) is 365.2422 days; the sidereal year (Earth's orbital period relative to distant stars) is 365.2564 days; the Gregorian civil year averages 365.2425 days per Pope Gregory XIII's 1582 reform (which inserted a 100/400-year leap-year correction to keep the calendar drift small over millennia — every 4th year is leap except century years not divisible by 400, so 2000 was leap but 1900 and 2100 are not). Practical applications: human lifespan (current global average 73 years per WHO 2024; US 78.4; Japan 84.3 per CDC NCHS Vital Statistics); ages and ISO 8601 date-of-birth notation; financial loan and bond terms (typical mortgage 15/30 years; corporate bond 1-30 years; US Treasury bonds 2-30 years); compound interest formulas A = P·(1+r/n)^(n·t) with t in years; warranty periods; climate-change projections per IPCC AR6 (2030/2050/2100 emissions pathway scenarios SSP1-1.9 to SSP5-8.5). Astronomical 'light-year' distance unit (9.461 × 10¹⁵ m) is derived from the Julian year.

Years are commonly used in scheduling, physics, project management, and scientific computing.

The Second (symbol: s) is a unit of time. The SI base unit of time per ISO 80000-3 §3-7 and BIPM SI Brochure 9th edition, defined since the 13th CGPM (1967) by the atomic transition of caesium-133: exactly 9,192,631,770 periods of the radiation between the two hyperfine levels of the ground state at 0 K under no external perturbation. The second is the most precisely realized SI unit — current state-of-the-art caesium fountain primary frequency standards (NIST-F2 at Boulder Colorado, PTB Braunschweig CSF2, INRIM ITCsF2, NICT-NMIJ) achieve fractional uncertainty 2 × 10⁻¹⁶ (the second drifts by less than 1 second over 150 million years); optical clocks based on Sr-87 lattice or Yb-171 ion approach 10⁻¹⁸ (1 second in age of universe). Seconds are the universal unit in physics and engineering; every derived unit involving time (m/s, W, Hz, N) builds on it. Practical applications: GPS positioning requires <100 ns timing accuracy per IS-GPS-200; telecom synchronization per IEEE 1588 PTP (Precision Time Protocol) provides sub-microsecond network sync; international UTC timekeeping per BIPM Circular T is computed from a weighted ensemble of ~400 atomic clocks at ~80 national metrology institutes worldwide.

Seconds are commonly used in scheduling, physics, project management, and scientific computing.