From: "Ciro Discepolo" <discepol@tin.it> Date: Fri, 13 Jul 2001 14:50:36 +0200
I have noted some little problems respect DST in Canada analyzing between Thomas Shanks data and the Time zone data
I finally got around to decoding your attachment (sorry, I don't use Microsoft Word, so Word documents are a bit of a pain for me). Thanks very much for taking the time to correct the errors in the timezone tables; you must have gone to a lot of work! I have the following reaction to your comments:
Halifax does not use DST in the year 1932, while in the 1950 and 1955 use a DST.
Thanks for catching this error; I'll fix this in my next proposed patch.
From 1942 to 1944 Shanks says that ST JOHNS saved 1 hour (war time), while in the timezone I've a normal DST from 1942 to 1944 without stop.
Here the timezone database was following Whitman rather than Shanks. However, Shanks seems more reliable about Canadian data than Whitman, so I'll change to Shanks here.
In the following table there are other date with difference from Shanks, TIMEZONE and SHANKS contains the offset from GMT in DATE TESTED.
ZONE DATE TESTED TIMEZONE SHANKS --------------------------------------------------------------------------- GOOSE BAY 15-1-1943 3,3 2,3 GOOSE BAY 15-1-1944 3,3 2,3
These discrepancies are for the same reason as St Johns, so changing St Johns will also remove these discrepancies.
GOOSE BAY 15-8-1917 2,3 3,3
NIPIGON 15-1-1941 5 4 NIPIGON 15-1-1942 5 4
THUNDER BAY 15-1-1941 5 4 THUNDER BAY 15-1-1942 5 4
RAINY RIV. 15-1-1941 6 5 RAINY RIV. 15-1-1942 6 5
REGINA 15-8-1958 6 7
Thanks for catching these transcription errors; I'll fix them too.
MONTREAL 15-8-1917 5 4
But Montreal uses Canadian table #119, which says: 25 Mar 1917 2:00 4:00 24 Apr 1917 0:00 5:00 This means daylight saving time was not observed after April 24 of that year, so it seems to me that the SHANKS column should be "5". Perhaps the discrepancy is because you are using a different edition of Shanks? I am using the Revised 5th edition of Shanks's International Atlas <http://astrocom.com/books/full/b112x.php>.
WINNIPEG 15-1-1942 6 5
But Winnipeg uses Canadian table #171, which says: 26 Sep 1937 2:00 6:00 9 Feb 1942 2:00 5:00 so Shanks is saying that daylight saving time was not observed until February 9 of that year, so the SHANKS column should say "6".
EDMONTON 15/08/1918 6 7
But Edmonton uses Canadian table #179, which defers to table #5 for 1918, and table #5 says: 14 Apr 1918 2:00 6:00 31 Oct 1918 2:00 7:00 so the SHANKS column should say "6".
DAWSON FROM 1947 TO 1972 8 9
The timezone table says that Dawson was at 9 from 1947 to 1965; this agrees with Shanks, who uses Canadian time table #253. But that "1947 TO 1972" suggests to me that you've confused Dawson with Dawson Creek. Dawson Creek uses Canadian time table #251 and was at 8 (7 during summer) from 1947 to 1972. Thanks again for checking the database; your fixes should appear in the next version.