When querying the time zone, the date command cannot deal with the hour when time changes from standard time to daylight saving time.  Below examples show the tests done in the Pacific time zone.

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date -d "20120311 01" +%:::z
-08

date -d "20120311 02" +%:::z
date: invalid date `20120311 02'

date -d "20120311 03" +%:::z
-07

date -d "20140309 01" +%:::z
-08

date -d "20140309 02" +%:::z
date: invalid date `20140309 02'

date -d "20140309 03" +%:::z
-07