Convert Years to Weeks

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 Week (symbol: wk) is a unit of time. A unit of time equal to exactly 7 days = 604,800 seconds. The seven-day week has cultural and religious roots predating most other time units — appearing independently in: ancient Babylonian astronomy (named for the seven 'classical planets' visible to the naked eye — Sun, Moon, Mars, Mercury, Jupiter, Venus, Saturn — preserved in modern English Sunday/Monday/Saturday and Romance-language Mardi/Mercredi/etc.); Jewish religious tradition (Sabbath/Shabbat seventh-day rest per Torah Genesis 2:2 and Exodus 20:8-11); Roman planetary week formalized by Emperor Constantine in 321 CE; Islamic Hijri calendar (Friday Jumu'ah congregational prayer per Qur'an 62:9). ISO 8601 formalizes week-numbering (ISO weeks W01-W52/W53, starting Monday). Practical applications: pay periods (US bi-weekly 2-week cycle most common; UK monthly; ECMA-376 Office Open XML date formats include week-of-year); gestational age in obstetrics per ACOG + RCOG (full-term 37-42 weeks; preterm <37 weeks); software-development sprint cycles per Scrum framework (1-4 week sprints, 2-week most common); academic terms (quarter ~10 weeks, semester ~15-17 weeks per US Department of Education credit-hour definition). Not an SI unit and not officially accepted for use alongside SI, but the most widely recognized calendar unit on Earth.

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