An easy way to print out two timezones side by side.

tz-diff.go

package main

import (
	"bytes"
	"flag"
	"fmt"
	"text/tabwriter"
	"time"
)

var flagZone = flag.String("z", "UTC", "remote time zone")

func init() {
	flag.Parse()
}

func main() {
	tz, e := time.LoadLocation(*flagZone)
	if e != nil {
		fmt.Println(e)
		return
	}

	now := time.Now()
	tt := time.Date(now.Year(), now.Month(), now.Day(), 0, 0, 0, 0, time.Local)

	buf := bytes.Buffer{}
	w := new(tabwriter.Writer)
	w.Init(&buf, 10, 0, 1, ' ', 0)
	fmt.Fprintf(w, "%s\t%s\n", tt.Location(), tz)
	fmt.Fprintln(w, "-------\t-------")

	for i := 0; i < 24; i++ {
		l := tt.Add(time.Duration(i) * time.Hour).Format("3:04pm")
		r := tt.In(tz).Add(time.Duration(i) * time.Hour).Format("3:04pm")
		fmt.Fprintf(w, "% 7s\t% 7s\n", l, r)
	}

	w.Flush()
	fmt.Println(buf.String())
}

Sample output:

Local     UTC
-------   -------
12:00am    7:00am
 1:00am    8:00am
 2:00am    9:00am
 3:00am   10:00am
 4:00am   11:00am
 5:00am   12:00pm
 6:00am    1:00pm
 7:00am    2:00pm
 8:00am    3:00pm
 9:00am    4:00pm
10:00am    5:00pm
11:00am    6:00pm
12:00pm    7:00pm
 1:00pm    8:00pm
 2:00pm    9:00pm
 3:00pm   10:00pm
 4:00pm   11:00pm
 5:00pm   12:00am
 6:00pm    1:00am
 7:00pm    2:00am
 8:00pm    3:00am
 9:00pm    4:00am
10:00pm    5:00am
11:00pm    6:00am