#compdef date

local -a args

if _pick_variant gnu="Free Software Foundation" unix --version; then
  args=(
    '-d[output specified date]:time string'
    '-f[output dates specified in file]:file:_files'
    '-I-[iso-8601]:precision:(date hours minutes seconds)'
    '-r[reference]:file:_files'
    '-R[rfc-2822]'
    '-s[set]:time string'
    '--rfc-3339=-[output date and time in RFC 3339 format]:output type:(date seconds ns)'
    --
    '*=FILE*:file:_files'
    '*=DATEFILE*:date file:_files'
  )
else
  case "$OSTYPE" in
    solaris*)
      args=( '-a:adjustment' )
    ;;
    freebsd*|darwin*)
      args=(
	'-n[only set time on current machine]'
	'-d:daylight saving time value'
	'-j[do not try to set date]'
	'-f:parsing format'
	'-r:seconds since epoch'
	'-t:minutes west of GMT'
	'-v:adjustment value'
      )
    ;;
    openbsd*)
      args=(
	'-n[only set time on current machine]'
	'-d:daylight saving time value'
	'-a[gradually skew]'
	'-r:seconds since epoch'
	'-t:minutes west of GMT'
      )
    ;;
  esac
fi

_arguments \
  '-u[display or set time in UTC]' \
  ': :_guard "^--*" "format or date"' \
  "$args[@]"