On 06/01/2015 11:53, Andrew James wrote:
As there are 24 leap years in three out of four centuries and 25 in the fourth,
in a 400 year period there are
303*365+97*366 = 146097 = 20871*7 days.
So the weekday pattern repeats every 400 years, as this is exactly 20871 weeks.
The relationship of weekdays to dates is such that the 13th of the month falls
more often on Friday in the 400 year period than on any other day of the week -
not a large bias, but one which doesn't go away! The 13th falls on Monday 685,
Tuesday 685, Wednesday 687, Thursday 684, Friday 688, Saturday 684, and Sunday
687 times.
Regards, Andrew James
Secure Meters (UK) Ltd. is a registered company in England: 2199653
Secure House, Moorside Road, Winchester, SO23 7RX
This correspondence is confidential and solely for the intended recipient(s). If you are not the intended recipient, you must not use, disclose, copy, distribute or retain this message or any part of it. If you are not the intended recipient please delete this correspondence from your system and notify the sender immediately.
---------------------------------------------------
https://lists.uni-koeln.de/mailman/listinfo/sundial
Just to clarify : The answer to the original question is that this
situation recurs every 28 years, so will have occurred in 1987, 1959,
1931, 1903 and 1874 (29 years because 1900 was not a leap year) and will
occur again in 2043, 2071, 2099 and 2128 (29 years because 2100 will not
be a leap year)
--
--
Richard Mallett
Eaton Bray, Dunstable
South Beds. UK
---------------------------------------------------
https://lists.uni-koeln.de/mailman/listinfo/sundial
