Week (wk)
Definition: A week is a unit of time equal to 7 days.
History/origin: The seven-day week has ancient roots in Babylonian, Jewish, Roman, and later Christian traditions, eventually becoming a global civil standard.
Current use: Weeks are used for payroll cycles, planning, school timetables, project tracking, and recurring schedules.
Year (yr)
Definition: The year is a long calendar unit based on Earth's solar orbit. For unit conversion, it is commonly averaged as 365.25 days.
History/origin: People organized years around seasons, planting cycles, and celestial observations, then refined them through calendars for civic and scientific use.
Current use: Yr is used for ages, anniversaries, mortgages, warranties, leases, climate averages, school grades, investment horizons, history timelines, and long-term records.