1600 (leap year in the Gregorian calendar)

Why 1600 is a century leap year

The Gregorian calendar modifies the simpler Julian rule for leap years to keep the calendar year aligned with the solar year. In the Gregorian system:

• Most years divisible by 4 are leap years (they include February 29).
• However, years that mark the end of a century (those divisible by 100) are not leap years unless they are also divisible by 400.

Since 1600 is divisible by 400, it meets the additional century requirement and is therefore a leap year in this calendar.

Calendar context and historical note

The Gregorian reform was introduced in 1582, but different countries adopted it at different times. When describing the day of the week for historical dates, some sources use the Gregorian calendar even for periods before a particular country adopted it; this practice is called using the proleptic Gregorian calendar. That is why one can state that 1600 began on a Saturday in the Gregorian system, while local practice at the time could have followed the Julian calendar in many places.

Related century years

Century years that are leap years in the Gregorian system occur every 400 years. Examples include:

• Year 1200, 1600, 2000 — all divisible by 400 and therefore leap years.
• Year 1700, 1800, 1900 — century years that are not leap years under the Gregorian rule because they are divisible by 100 but not by 400.