Date command is not working properly

IMPe · March 30, 2014, 5:34am

Hi,

in my script, i take the last month by

a=$(date --date '1 month ago' +%Y%m)

i expect that it give me in this month "March" as result 201402,
but linux gave me 201403.

IMPe@ABC123:> ~/date --date '1 month ago' +%Y%m
201403

i'm reasonably confused. Any idea?

Thanks in advance,
IMPe

PS.:
System
Linux ABC123 3.11.10-7-desktop #1 SMP PREEMPT Mon Feb 3 09:41:24 UTC 2014 (750023e) x86_64 x86_64 x86_64 GNU/Linux

Scrutinizer · March 30, 2014, 6:34am

Hi, try:

date --date="$(date +%Y%m15) 1 month ago" +%Y%m

This behavior occurs, because februari 30 does not exist. So it is best to use the middle of the month to calculate the previous month..

--
Interestingly in recent ksh93 this seems to work alright:

$ printf "%(%Y%m)T\n" "last month"
201402

IMPe · March 30, 2014, 9:38am

scrutinizer:

Hi, try:
date --date="$(date +%Y%m15) 1 month ago" +%Y%m
This behavior occurs, because februari 30 does not exist. So it is best to use the middle of the month to calculate the previous month..

Interestingly in recent ksh93 it seems to work alright:
$ printf "%(%Y%m)T\n" "last month"
201402

Thanks a lot Scrutinizer! I thought that this command i used is working exactly -
unfortunatelly it doesn't.
Thank you,
IMPe