How Rare?

This is puzzling:

The convergence of Thanksgiving and the first day of Hanukkah is something that happens incredibly rarely, and this Thursday will be a once in a many-lifetime event.

Nov. 28 will be the first time - almost ever - that the two holidays will share the same date on the calendar, and according to LiveScience, it won't happen again about 70,000 years, and it hasn't happened since the late 19th century.

No one knows exactly how long, because the calendars aren't going up that high," Rabbi Jason Miller told LiveScience.

The overlap this year is because according to the Jewish calendar, this is a leap year, meaning that an entire extra month is added to the calendar. Because of that, most major Jewish holidays moved up by nearly a month.

Couple that with the extremely late date of Thanksgiving in 2013, and you've got a convergence of holidays that comes once in many, many generations.

Consider the following:

Since Thanksgiving is the 4th Thursday in November, it can only occur on one of the seven dates, Nov. 22 thru Nov.28.

Hannukkah will fall from late November to late December, say about 32 different dates.

The probability of the two dates share the same calendar date in any one year is 7x32 or once every 224 years.

OK. Because of the extra month leap year variation in the Jewish calendar, let's double 32 different dates to 64 different dates.

Then the probability of the two holidays falling on the same date is 7x64=448. Once ever 448 years.

The statement, "It hasn't happened since the late 19th century" would make sense.

But the statement, "It won't happen again about 70,000 years" ???

Now how do you figure that? :confused: