Calculate Leap Years

Hebrew Calendar Leap Years

• During a Hebrew calendar leap year, an additional month of Adar is added.
• There are seven leap years in every 19 years.
• The 3rd, 6th, 8th, 11th, 14th, 17th, and 19th years of the 19-year Metonic cycle are leap years.
• 5785 is the 9th year of the 19-year Metonic cycle and is therefore not a leap year.
• After 5785, the next leap year is 5787 – the 11th year of the cycle.
• A mnemonic for remembering the years corresponding to leap years is: "גוחאדז"ט". The Hebrew letters Gimmel, Vav, Chet, Aleph, Dalet, Zayin, and Tet are used to represent the Hebrew numerals, 3, 6, 8, 1, 4, 7, 9.
• Mathematically, it can be determined if a year is a leap year by determining whether ((7*year)+1) mod 19) is less than 7.
• During a leap year, there are 13 months, a total of 383, 384, or 385 days (depending on whether Cheshvan and/or Kislev have 29 or 30 days). During a non-leap year, there are 12 months, a total of 353, 354, or 355 days.

Gregorian Calendar Leap Years

• During a Gregorian calendar leap year, an additional day is added to February.
• A Gregorian year is a leap year if it meets BOTH criteria:
  • It is divisible by 4.
  • It is not divisible by 100, unless it is also divisible by 400.
• 2024 is divisible by 4 and not by 100, and is therefore a leap year.
• After 2024, the next leap year is 2028. 2028 is divisible by 4 and not by 100, and is therefore a leap year.
• During a leap year, there are 366 days. During a non-leap year, there are 365 days.