Dear Claude et al,
We published an article by Robert Hannah on this topic in the BSS Bulletin:
R. Hannah: 'The Pantheon as a Timekeper', BSS Bull., 21(iv), pp. 2-4 (Dec 2009).
It is available in downloadable form on the BSS website at
http://sundialsoc.org.uk/publications/the-bss-bulletin/
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
Merry 358 and Happy 1, or is it Merry 357 and Happy 0 :)
On 2015-01-06 18:07, John Pickard wrote:
If nothing else, the replies show that dates are rather tricky things
with some interesting mathematics behind them. Wouldn't it be simpler
to move to decimal time and a decimal calendar? (NOT a
Good morning everyone,
Many thanks for the replies to my (slightly trivial) question re Fri 13. I
now have a better understanding of how to predict which days to stay in bed,
avoid walking under ladders, and not kicking black cats!
If nothing else, the replies show that dates are rather
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
