ou en ksh :


--- cut here for tz.sh ---
#!/bin/ksh
# Usage tz.sh N [fmt_string]
# Where N is how many days to go backward
# fmt_string is optional format arg to date command

days=$1;shift

date "+%H %Z" | read t1 tn
t0=$(TZ=0 date +%H)
(( delta = t0 - t1 ))
(( adjust = delta + 24 * days ))

TZ="$tn$adjust" date "$@"

--- end of tz.sh ---

tz.sh 1 # gives you the date and time 24 hours ago
tz.sh 1 '+%d' # gives you just yesterday's day of the month
tz.sh 1 '+%Y%m%d' # gives you yesterday as yyyymmdd
tz.sh -1 # gives you tomorrow


source : comp.unix.aix : http://groups.google.fr/groups?hl=fr&lr=&ie=UTF-8&oe=UTF-8&threadm=d1c185ef.0201230015.4078df0%40posting.google.com&rnum=7&prev=/&frame=on