Ed Pegg Jr.:

> {350, 357, 378, 385}

> I used Mathematica to find the number of days between successive Easters.
> To my surprise, the separation was always one of the above four numbers, at
> least in the time span 1000 - 3000.

One would expect the time between Easters to be 12 or 13 moon months.

With a moon period of ~29.53 days we get
12 moon months 354.36 days
13 moon months 383.89 days

Since Easter is always Sunday, the days between must be a multiple of 7.
Thus Ed's 4 ranges are the expected.

It still might require some time with the PFM formula to make sure those
are the only separations possible.

I would expect from this that 385 is much more common than 378 and that
350,357 are more common than 378,385. How does this compare with Ed's results?

Christian