linux touch relative time giving wrong result-CodePudding

I'm using bash touch to change the date and time of a file. It works correctly if I simply specify the date and time. If, however, I use a relative time I get unexpected behavior.

$ date -R -r test.txt
Sat, 28 May 2022 02:56:22 -0400
$ touch -d '27 May 2022 05:31:12' test.txt
$ date -R -r test.txt
Fri, 27 May 2022 05:31:12 -0400
$ touch -d '27 May 2022 05:31:12 - 1 hour' test.txt
$ date -R -r test.txt
Fri, 27 May 2022 03:31:12 -0400
$ touch -d "27 May 2022 05:31:12   1 hour" test.txt
$ date -R -r test.txt
Fri, 27 May 2022 01:31:12 -0400

Note that although I asked for 1 hour earlier and then 1 hour later, it gave 2 hours earlier and 4 hours earlier respectively. Any help would be appreciated.

CodePudding user response：

When you do your touch, you do no specify the timezone. If you do, all your date arithmetic works ok.

EX:

$ touch -d '27 May 2022 05:31:12' test.txt
$ date -R -r test.txt
Fri, 27 May 2022 05:31:12 -0400
$
$ touch -d '27 May 2022 05:31:12 -0400 - 1 hour' test.txt
$ date -R -r test.txt
Fri, 27 May 2022 04:31:12 -0400