tag 15752 notabug thanks On 10/29/2013 07:58 PM, Andy Lamb wrote: > Hello, > > February of 2013 does not work, it comes up with March twice! > > /bin/date --date=-6 month +%b%Y = Apr2013 > /bin/date --date=-7 month +%b%Y = Mar2013 > /bin/date --date=-8 month +%b%Y = Mar2013 > /bin/date --date=-9 month +%b%Y = Jan2013
This is a FAQ: https://www.gnu.org/software/coreutils/faq/coreutils-faq.html#The-date-command-is-not-working-right_002e Subtracting by months is fuzzy (does it mean multiples of 28, 29, 30, or 31 days? What is one month after Oct 31, Nov 30 or Dec 1?). Daylight Savings doesn't help (even if I subtract an exact multiple of days, there are cases where a timezone could cause a multiple of 24 hours to bypass a 23-hour day or get trapped by a 25-hour day). You are best off trying to start from a middle of a month to guarantee that even with the fuzz you still land in the desired destination. $ date --date="$(date "+%b 15") -6 month" +%b%Y Apr2013 $ date --date="$(date "+%b 15") -7 month" +%b%Y Mar2013 $ date --date="$(date "+%b 15") -8 month" +%b%Y Feb2013 $ date --date="$(date "+%b 15") -9 month" +%b%Y Jan2013 As such, I'm closing this as not a bug, although you may feel free to add further comments. -- Eric Blake eblake redhat com +1-919-301-3266 Libvirt virtualization library http://libvirt.org
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