In uk.sci.astronomy message
..co.uk, Thu, 14 Feb 2008 21:05:04, p forsdick
posted:

I have been working on a spreadsheets of dates for Easter from 1593 to 2999
by date and have noticed something. Does anybody know why, on many
occasions the same easter date is often 11 years apart
for example easter day on march 30 occured in 1975 1986 and 1997 then a gap
of 62 years then 2059 2070 and 2081 and 2092
in fact there are 54 Easters in this period for march 30 and on 38 occasions
they are 11 years after a previous one, The next highest gap is 62 years
which has 7 occasions.
this is puzzling me
also taking 23rd March which is this years easter and only occurs these 13
times the number 152 years comes up 4 times 1636 1704 1788 1845 1856 1913
2008 2160 2228 2380 2532 2600 and 2752
the 152 year gaps are 2008-2160, 2228-2380 2380 -2532 and 2600-2752
if any body wants a copy of this sheet only complete to March 30 so far
please let me know

See whether URL:http://www.merlyn.demon.co.uk/estrdate.htm and
associated pages help with your questions. See also my test program in
URL:http://www.merlyn.demon.co.uk/programs/mjd_date.zip, which can
calculate various related matters.

The site includes a new fast routine traceable to the Prayer Book.

The possible intervals between Gregorian Easters of the same date of the
year are : 5 6 11 17 35 40 46 51 57 62 63 68 73 79 84 95 119 125 130 141
147 152 163 179 209 220 231 247 277 288 293 299 304 315 372 383 451 467
524 535 592 603 671 676 687 755 896 907 975 991 1059 1127 1279 1363 1431
1499 1583 1651 1803 1887 years (I consider the range of 5700000 years
starting at 2000; Easter repeats every 5700000 years).

One might consider, rather than the Month-Day date, the (ISO) Week-Day
date (simpler, because Day is invariably 7), and the Ordinal Date.


The shorter date repeat intervals, at least, are strongly influenced by
the possible intervals between Sundays having the same date of the year.
The smallest intervals for that are 5 & 6 years (with 2 or 1 Leap Days
included) and the next must be 11 years.

--
(c) John Stockton, nr London, UK. Turnpike v6.05 MIME.
Web URL:http://www.merlyn.demon.co.uk/ - FAQqish topics, acronyms & links;
Astro stuff via astron-1.htm, gravity0.htm ; quotings.htm, pascal.htm, etc.
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