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Hi John and All!
Happy 2015!
As March and November always start on the same day of the week, each year this
back-to-back Friday the 13th happens, also happens in November. So years like
2015 should be trice as lucky or unlucky - with three Friday the 13ths,
depending on how one looks at them.
Here are years from the mid-20th to mid-21st centuries in which this happens:
1953, 1959, 1970, 1981, 1987, 1998, 2009, 2015, 2026, 2037, 2043, 2054, 2065
As each year is roughly 52w, 1d the day of the week that the year and each
month starts moves forward a day each year. But moving two days forward on
from LYD through the end of the following February.
Thus, the pattern of what years we get Feb/Mar (and Nov) Friday the 13ths and a
lot of other repeating calendar dates is typically every six or eleven years.
Typically in an 11, 11, 6, 11, 11, 6.... cycle.
This is due to Leap Years typically happening every four years (with centennial
LY exceptions), we will typically see one Leap Year in each seven years (7-1 =
6), and three Leap Years in two fourteen year ( (2x7) - 3 = 11) cycle. Note
also that 11 + 11 + 6 = 28 (four full weeks the calendar has advanced). Thus
allowing for the cycle to repeat (with centennial LY exceptions).
At the end of the 21st century when 2100 is not a Leap Year, the years we'll
see three Friday the 13ths are ....2082, 2093, 2099, 2105, 2111, 2116, 2122,
2133, 2139, 2150, 2161, 2167, 2178, 2189, 2195..... In which case we see a
pattern of 11, 6, 6, 6, 6, 6, 11, 6, before resuming the 11, 11, 6 pattern...
Hope that helps.
Cheers,
Thad
45.3N 73.1W
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On Mon, 1/5/15, John Pickard <john.pick...@bigpond.com> wrote:
Subject: Friday 13 and Friday 13
To: "Sundial List" <sundial@uni-koeln.de>
Received: Monday, January 5, 2015, 4:35 PM
Good morning all, and a happy 2015 to
everyone.
Looking at my diary this morning, I noticed that 2015 is a
bit unusual in
having Friday 13 in consecutive months: February and March.
Does anyone know how often this occurs, when was the last
time, and when is
the next time it will happen?
(And no, I don't place any particular significance in the
day!)
Cheers, John
John Pickard
john.pick...@bigpond.com
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