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Subject:	date function: how many days in october are there?
Date:	Thu, 29 Sep 2005 21:41:03 -0600
Message-ID:	<3C46C4ED0F9B944690547357EB7F1C0FF430@COFORTCOL2S304.agwest.one.usda.gov>
From:	"Pagano, Tom - Portland, OR" <tom DOT pagano AT por DOT usda DOT gov>
To:	<cygwin AT cygwin DOT com>
X-MIME-Autoconverted:	from base64 to 8bit by delorie.com id j8U3f7Ud024810

I've noticed that the date function does something strange trying to access October 31st in a statement like 
 
$ date -d "1970-10-01 +1 month -1 day"
as opposed to something like 
$ date -d "1970-11-01 -1 day"
which (I think??) should be functionally equivalent. The actual results of the 2nd are obviously preferrable to the 1st... but I do note something squirrly going on with the hours in both (daylight savings time?) 
 
When I run date -d "$i-10-01 +1 month -1 day" I get 
Tue Oct 31 00:00:00 PST 1950
Wed Oct 31 00:00:00 PST 1951
Fri Oct 31 00:00:00 PST 1952
Sat Oct 31 00:00:00 PST 1953
Sun Oct 31 00:00:00 PST 1954
Mon Oct 31 00:00:00 PST 1955
Wed Oct 31 00:00:00 PST 1956
Thu Oct 31 00:00:00 PST 1957
Fri Oct 31 00:00:00 PST 1958
Sat Oct 31 00:00:00 PST 1959
Mon Oct 31 00:00:00 PST 1960
Tue Oct 31 00:00:00 PST 1961
Wed Oct 31 00:00:00 PST 1962
Thu Oct 31 00:00:00 PST 1963
Sat Oct 31 00:00:00 PST 1964
Sun Oct 31 00:00:00 PST 1965
Mon Oct 31 00:00:00 PST 1966
Tue Oct 31 00:00:00 PST 1967
Thu Oct 31 00:00:00 PST 1968
Fri Oct 31 00:00:00 PST 1969
Fri Oct 30 23:00:00 PST 1970
Sun Oct 31 00:00:00 PDT 1971
Mon Oct 30 23:00:00 PST 1972
Tue Oct 30 23:00:00 PST 1973
Wed Oct 30 23:00:00 PST 1974
Thu Oct 30 23:00:00 PST 1975
Sun Oct 31 00:00:00 PDT 1976
Sun Oct 30 23:00:00 PST 1977
Tue Oct 30 23:00:00 PST 1979
Thu Oct 30 23:00:00 PST 1980
Fri Oct 30 23:00:00 PST 1981
Sun Oct 31 00:00:00 PDT 1982
Sun Oct 30 23:00:00 PST 1983
Tue Oct 30 23:00:00 PST 1984
Wed Oct 30 23:00:00 PST 1985
Thu Oct 30 23:00:00 PST 1986
Fri Oct 30 23:00:00 PST 1987
Sun Oct 30 23:00:00 PST 1988
Mon Oct 30 23:00:00 PST 1989
Tue Oct 30 23:00:00 PST 1990
Wed Oct 30 23:00:00 PST 1991
Fri Oct 30 23:00:00 PST 1992
Sun Oct 31 00:00:00 PDT 1993
Sun Oct 30 23:00:00 PST 1994
Mon Oct 30 23:00:00 PST 1995
Wed Oct 30 23:00:00 PST 1996
Thu Oct 30 23:00:00 PST 1997
Fri Oct 30 23:00:00 PST 1998
Sun Oct 31 00:00:00 PDT 1999
Mon Oct 30 23:00:00 PST 2000
Tue Oct 30 23:00:00 PST 2001
Wed Oct 30 23:00:00 PST 2002
Thu Oct 30 23:00:00 PST 2003
Sun Oct 31 00:00:00 PDT 2004
Sun Oct 30 23:00:00 PST 2005
Mon Oct 30 23:00:00 PST 2006
Tue Oct 30 23:00:00 PST 2007
Thu Oct 30 23:00:00 PST 2008
Fri Oct 30 23:00:00 PST 2009
Sun Oct 31 00:00:00 PDT 2010
Sun Oct 30 23:00:00 PST 2011
Tue Oct 30 23:00:00 PST 2012
Wed Oct 30 23:00:00 PST 2013
Thu Oct 30 23:00:00 PST 2014
Fri Oct 30 23:00:00 PST 2015
 
as opposed to date -d "$i-11-01 -1 day"
Tue Oct 31 00:00:00 PST 1950
Wed Oct 31 00:00:00 PST 1951
Fri Oct 31 00:00:00 PST 1952
Sat Oct 31 00:00:00 PST 1953
Sun Oct 31 00:00:00 PST 1954
Mon Oct 31 00:00:00 PST 1955
Wed Oct 31 00:00:00 PST 1956
Thu Oct 31 00:00:00 PST 1957
Fri Oct 31 00:00:00 PST 1958
Sat Oct 31 00:00:00 PST 1959
Mon Oct 31 00:00:00 PST 1960
Tue Oct 31 00:00:00 PST 1961
Wed Oct 31 00:00:00 PST 1962
Thu Oct 31 00:00:00 PST 1963
Sat Oct 31 00:00:00 PST 1964
Sun Oct 31 00:00:00 PST 1965
Mon Oct 31 00:00:00 PST 1966
Tue Oct 31 00:00:00 PST 1967
Thu Oct 31 00:00:00 PST 1968
Fri Oct 31 00:00:00 PST 1969
Sat Oct 31 00:00:00 PST 1970
Sun Oct 31 01:00:00 PDT 1971
Tue Oct 31 00:00:00 PST 1972
Wed Oct 31 00:00:00 PST 1973
Thu Oct 31 00:00:00 PST 1974
Fri Oct 31 00:00:00 PST 1975
Sun Oct 31 01:00:00 PDT 1976
Mon Oct 31 00:00:00 PST 1977
Wed Oct 31 00:00:00 PST 1979
Fri Oct 31 00:00:00 PST 1980
Sat Oct 31 00:00:00 PST 1981
Sun Oct 31 01:00:00 PDT 1982
Mon Oct 31 00:00:00 PST 1983
Wed Oct 31 00:00:00 PST 1984
Thu Oct 31 00:00:00 PST 1985
Fri Oct 31 00:00:00 PST 1986
Sat Oct 31 00:00:00 PST 1987
Mon Oct 31 00:00:00 PST 1988
Tue Oct 31 00:00:00 PST 1989
Wed Oct 31 00:00:00 PST 1990
Thu Oct 31 00:00:00 PST 1991
Sat Oct 31 00:00:00 PST 1992
Sun Oct 31 01:00:00 PDT 1993
Mon Oct 31 00:00:00 PST 1994
Tue Oct 31 00:00:00 PST 1995
Thu Oct 31 00:00:00 PST 1996
Fri Oct 31 00:00:00 PST 1997
Sat Oct 31 00:00:00 PST 1998
Sun Oct 31 01:00:00 PDT 1999
Tue Oct 31 00:00:00 PST 2000
Wed Oct 31 00:00:00 PST 2001
Thu Oct 31 00:00:00 PST 2002
Fri Oct 31 00:00:00 PST 2003
Sun Oct 31 01:00:00 PDT 2004
Mon Oct 31 00:00:00 PST 2005
Tue Oct 31 00:00:00 PST 2006
Wed Oct 31 00:00:00 PST 2007
Fri Oct 31 00:00:00 PST 2008
Sat Oct 31 00:00:00 PST 2009
Sun Oct 31 01:00:00 PDT 2010
Mon Oct 31 00:00:00 PST 2011
Wed Oct 31 00:00:00 PST 2012
Thu Oct 31 00:00:00 PST 2013
Fri Oct 31 00:00:00 PST 2014
Sat Oct 31 00:00:00 PST 2015

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