"date -d '-X day' returning wrong day around StandardTime/DaylightTime change-over

[Philip Zimmerman (phzimmer)]

Hello,

 

I've noticed  a behavior of the 'date' utility as a result of the DST 
change-over, and was wondering whether this is "expected behavior" or whether 
this is a problem, so I'm inquiring whether anyone else has noticed this.

 

During the StandardTime-DaylightTime changeover, the timeZone was correctly 
changed and the time reported by 'date' was correct during the change-over, 
however, it seems to be reporting the wrong day when using syntax to produce a 
date string using 'date -d '-X day' +%m/%d/%Y', where X is the number of days 
behind the change-over from Standard Time to Daylight Savings.  

 

i.e. For the EST to EDT changeover, If the current time is set to Monday Mar 
9th, 00:30, then:

date -d '-0 day' +%m/%d/%Y  reports 03/09/2009   (as it should)

date -d '-1 day' +%m/%d/%Y  reports 03/07/2009   (one day off)

 

If I set the time to Monday Mar 9th, 01:30 hours and do the same calculation, 
then it reports the correct day on both calculations. 

 

Tks -- pz