Shell Programming and Scripting

$ TZ=EDT+172 date +%F
2012-12-13

$ uname -a
AIX 1 7 000B29AAD400

$ uname -a
Linux 2.6.18-308.11.1.el5 x86_64 x86_64 x86_64 GNU/Linux

$ TZ=EDT+172 date +%F
2012-12-19

date -d

function date
{
  local t="${TZ%%[-0-9+]*}"
  local n="${TZ#$t}"
  [ -z "$t" ] && { command date "$@"; return; }
  #TZ=$t$((n%24)) /bin/date -d "$((-n/24)) days" "$@"
  TZ=$t$((n%24)) command date -d "$((-n/24)) days" "$@"
}

awk '{
  if (match($0, /TZ=[A-Z]+[-+0-9 ]+date/)) {
    n = s = substr($0, RSTART, RLENGTH)
    gsub(/[^-+0-9]/, "", n)
    sub(n, sprintf("%+d", n%24), s)
    x = sprintf("%+d days", -int(n/24))
    $0 = substr($0,1,RSTART-1) s " -d \"" x "\"" substr($0,RSTART+RLENGTH)
  }
  print
}'

date -d