One of my students from New York turns 6 today, maybe 7. But, he was my student starting 16 years ago. How’s that for a math riddle early in the morning?

If you take a look at the calendar though, the answer should be pretty clear. Charles is one of those lucky folk born on February 29, and so while he is now in his late 20s, he is also only 6 or 7. His actual birthday, of course, only comes around every 4 years. So, happy birthday to you, and other February 29 babies out there!

This year, we have a confluence though, making it even more fun. While the Gregorian Leap Year comes around every 4 years, the Hebrew Leap Year occurs 7 times in a 19-year cycle. And, rather than adding a single day, our calendar adds an entire month–we add Adar Alef, giving us twice the Adar as a normal year.

Thanks to the Facebook page Hebrew Calendar Facts (yes, it exists, you’re welcome!), here are some fun facts and numbers about this coincidence:

  1. Whenever a Hebrew leap year overlaps with a Gregorian leap year, the leap day *always* falls during the leap month. (Or at least it will for the next 4000+ years, until the Hebrew calendar drifts far enough.)
  2. 7 years out of every 76-year period are double leap years (Hebrew and Gregorian)
  3. More specifically, within each 76-year period (starting with Hebrew year 1), the double leap years are in years 8, 36, 44, 52, 60, 68, and 76. As you can see, they’re not evenly distributed: usually they’re 8 years apart, but there is also a 28-year gap in the cycle.
  4. Years that are divisible by 100 but not divisible by 400 (like 1700, 1800, and 1900) are *not* Gregorian leap years. So, if one of those years occurs at the right point in the 76-year cycle, then the gap between consecutive double leap years can be as much as 36 years.
  5. This year (2024/5784) is year 8 in the 76-year cycle. So the last time we had a double leap year was 8 years ago in 2016 (and 8 years before that in 2008, and 8 years before that in 2000, etc.), but we’re about to enter that 28-year gap, and the next double leap year won’t be until 2052.

Happy Leap Day to all of us–I am thinking about writing myself a note to open, God-willing, in 2052. How about you?

— Rabbi Sari Laufer