dt - display current date/time in various time zones

dt

#!/bin/bash
#
# dt: display useful date/time info incl current time in various time zones
#
# Any optional extra args are passed along to 'date'.
#
# usage examples:
#
#  $ dt
#  $ dt --date '3 hours ago'
#
# Hour listing inspired by https://github.com/oz/tz
#

show () {
    tz=$1; shift
    place=$1; shift

    echo -n "$(TZ=$tz date +'%H:%M %a' "$@") "
    printf "%-9s " $place

    hour=$(TZ=$tz date +%k "$@")
    for i in {-6..6}; do
	if [ $i -eq 0 ]; then echo -n $bold; fi
	printf "%02d" $((($hour+$i+24)%24))
	if [ $i -eq 0 ]; then echo -n $sgr0; fi
	echo -n " "
    done
    echo " $(TZ=$tz date +'%4Z (UTC%z)' "$@")"

}

bold=$(tput bold)
sgr0=$(tput sgr0)

echo
/usr/bin/cal -3
echo

show Australia/Sydney Sydney    "$@"
show Asia/Tokyo       Japan     "$@"
show Asia/Shanghai    China     "$@"
show Indian/Reunion   Reunion   "$@"
show Europe/Paris     France    "$@"
show Europe/London    London    "$@"
show UTC              UTC       "$@"
show US/Eastern       Boston    "$@"
show US/Central       Chicago   "$@"
show Canada/Mountain  Edmonton  "$@"
show Canada/Pacific   Vancouver "$@"

echo

Inspired by oz/tz, updated to include a list of recent/upcoming hours in each tz:

   December 2021          January 2022         February 2022
Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa  Su Mo Tu We Th Fr Sa
          1  2  3  4                     1         1  2  3  4  5
 5  6  7  8  9 10 11   2  3  4  5  6  7  8   6  7  8  9 10 11 12
12 13 14 15 16 17 18   9 10 11 12 13 14 15  13 14 15 16 17 18 19
19 20 21 22 23 24 25  16 17 18 19 20 21 22  20 21 22 23 24 25 26
26 27 28 29 30 31     23 24 25 26 27 28 29  27 28
                      30 31

08:48 Mon Sydney    02 03 04 05 06 07 08 09 10 11 12 13 14  AEDT (UTC+1100)
06:48 Mon Japan     00 01 02 03 04 05 06 07 08 09 10 11 12   JST (UTC+0900)
05:48 Mon China     23 00 01 02 03 04 05 06 07 08 09 10 11   CST (UTC+0800)
01:48 Mon Reunion   19 20 21 22 23 00 01 02 03 04 05 06 07   +04 (UTC+0400)
22:48 Sun France    16 17 18 19 20 21 22 23 00 01 02 03 04   CET (UTC+0100)
21:48 Sun London    15 16 17 18 19 20 21 22 23 00 01 02 03   GMT (UTC+0000)
21:48 Sun UTC       15 16 17 18 19 20 21 22 23 00 01 02 03   UTC (UTC+0000)
16:48 Sun Boston    10 11 12 13 14 15 16 17 18 19 20 21 22   EST (UTC-0500)
15:48 Sun Chicago   09 10 11 12 13 14 15 16 17 18 19 20 21   CST (UTC-0600)
14:48 Sun Edmonton  08 09 10 11 12 13 14 15 16 17 18 19 20   MST (UTC-0700)
13:48 Sun Vancouver 07 08 09 10 11 12 13 14 15 16 17 18 19   PST (UTC-0800)

(current day and hour are boldfaced, but that doesn't seem to survive cut/paste)