Simple time conversion script for a number of time zones in reference to local timezone

convert_time.sh

#!/bin/bash

# pass date as argument, empty is today
ref=$1

# fill this list with timezones you are interested in; first element is reference timezone
zones[1]=`cat /etc/timezone`
zones[2]="Europe/London"
zones[3]="Asia/Calcutta"
zones[4]="Asia/Tokyo"
zones[5]="America/Los_Angeles"
zones[6]="America/Montreal"

date -d "$ref" +'%a %D (%Z %:z)'
for zone in "${zones[@]}"; do
  printf "%-11s" `echo $zone|sed 's/.*\///;s/.*\(.\{10\}\)/…\1/'`
  # show converted time for timeslots from 8am to 5pm
  for time in `seq 8 17`; do
    echo -n " "$(TZ=$zone date -d "TZ=\"${zones[1]}\" $ref $time:00" +%H:%M)
  done
  # compute and show difference with local timezone
  diff=$(expr $(printf "%g" `TZ=$zone date +%z`) - $(printf "%g" `date +%z`)|sed 's/..$/:&/;s/^/+/;s/^+-/-/')
  if [ "$diff" != +0 ]; then
    echo " ($diff)"
  else
    echo
  fi
done