Timezone conversion by command line

Question

I know about http://www.timeanddate.com/worldclock/converter.html

I can't figure out how to query http://www.google.com in a sane natural format like "5pm BST in PST".

Or do I have to write such an app?

Solution 1

It's 6pm in Taipei, what time is it here?

date --date='TZ="Asia/Taipei" 18:00'
Fri Jul 16 11:00:00 BST 2010

At 11am here in London, what time is it in Taipei?

TZ=Asia/Taipei date -d "11:00 BST"
Fri Jul 16 18:00:00 CST 2010

Solution 2

I think this is closer to what the OP asked (Since he doesn't necessarily know that BST is Taipei? and the answer doesn't explain how to get to "Asia/Taipei" from 'BST').

First my current date:

$ date
Mon Apr 21 13:07:21 MDT 2014

Then the date I want to know:

$ date -d '5pm BST'
Mon Apr 21 15:00:00 MDT 2014

So I know that 5pm BST is 2 hours away.

I usually forget if I have to add or remove two hours from EDT times so I have a little script with the common timezones I have to work with:

$ cat tz
#!/bin/bash
TZ='America/Edmonton' date
TZ='America/Chicago' date
TZ='America/New_York' date

And the output:

$ tz
Mon Apr 21 13:12:32 MDT 2014
Mon Apr 21 14:12:32 CDT 2014
Mon Apr 21 15:12:32 EDT 2014

Valid locations for your tz script can be found here /usr/share/zoneinfo.

But again, for times in the future I just use date -d '<time> <timezone>'.

Solution 3

This example is from http://www.pixelbeat.org/cmdline.html#dates

It gives the local time corresponding to 9AM on the west coast of the US, accounting for differing day light savings transitions.

date --date='TZ="America/Los_Angeles" 09:00 next Fri'

Use tzselect to get the TZ. The PST format is ambiguous. IST = Indian Standard Time and Irish Summer Time for example.

Solution 4

I know it is an old thread, but I needed a code for the same use case and, based on the ideas here, developed this little bash script:

#!/bin/bash
# ig20180122 - displays meeting options in other time zones
# set the following variable to the start and end of your working day
myday="8 20" # start and end time, with one space
# set the local TZ
myplace='America/Sao_Paulo'
# set the most common places
place[1]='America/Toronto'
place[2]='America/Chicago' # Houston as well
place[3]='Europe/Amsterdam'
place[4]='Europe/Dublin'
# add cities using place[5], etc.
# set the date format for search
dfmt="%m-%d" # date format for meeting date
hfmt="+%B %e, %Y" # date format for the header
# no need to change onwards
format1="%-10s " # Increase if your cities are large
format2="%02d "
mdate=$1
if [[ "$1" == "" ]]; then mdate=`date "+$dfmt"`; fi
date -j -f "$dfmt" "$hfmt" "$mdate"
here=`TZ=$myplace date -j -f "$dfmt" +%z  "$mdate"`
here=$((`printf "%g" $here` / 100))
printf "$format1" "Here" 
printf "$format2" `seq $myday` 
printf "\n"
for i in `seq 1 "${#place[*]}"`
do
    there=`TZ=${place[$i]} date -j -f "$dfmt" +%z  "$mdate"`
    there=$((`printf "%g" $there` / 100))
    city[$i]=${place[$i]/*\//}
    tdiff[$i]=$(($there - $here))
    printf "$format1" ${city[$i]}
    for j in `seq $myday`
    do
        printf "$format2" $(($j+${tdiff[$i]}))
    done
    printf "(%+d)\n" ${tdiff[$i]}
done

You can either use to check the time differences today or in a future date:

16:08 $ meet
January 22, 2019
Here       08 09 10 11 12 13 14 15 16 17 18 19 20 
Toronto    05 06 07 08 09 10 11 12 13 14 15 16 17 (-3)
Chicago    04 05 06 07 08 09 10 11 12 13 14 15 16 (-4)
Amsterdam  11 12 13 14 15 16 17 18 19 20 21 22 23 (+3)
Dublin     10 11 12 13 14 15 16 17 18 19 20 21 22 (+2)
16:13 $ meet 05-24
May 24, 2019
Here       08 09 10 11 12 13 14 15 16 17 18 19 20 
Toronto    07 08 09 10 11 12 13 14 15 16 17 18 19 (-1)
Chicago    06 07 08 09 10 11 12 13 14 15 16 17 18 (-2)
Amsterdam  13 14 15 16 17 18 19 20 21 22 23 24 25 (+5)
Dublin     12 13 14 15 16 17 18 19 20 21 22 23 24 (+4)
16:13 $ 

HTH

Solution 5

Use Wolfram Alpha. To the basic URL…

http://www.wolframalpha.com/input/?i=

append the conversion, with spaces replaced by +. For example:

http://www.wolframalpha.com/input/?i=5+PM+CET+to+PST

Note that Wolfram Alpha does not seem to recognize BST as a time zone.

View more solutions

Comments

[Dal Hundal]

What do you mean exactly? Command line linux? Command you can type into Google? What?!

[hendry]

command line in shell and google's query box are both a command line to me

[hendry]

perhaps a better tool would do cities by airport codes, 5pm LHR in SFO

[hroptatyr]

@hendry dateutils can do timezone conversion based on iata and icao airport codes: dateconv 2017-05-16T17:00 --from-zone iata:SFO --zone iata:LHR -> 2017-05-17T01:00:00

[hendry]

Didn't know about tzselect, thanks. If you enter wrong 'TZ' input you can get misleading results, e.g. TZ=London date Fri Jul 16 10:28:52 London 2010

[hendry]

how does one quickly look up time zone codes?

[DavidGamba]

@hendry This is a cool interactive online map: timeanddate.com/time/map/#!cities=241

[Ben]

Strange, but the first way doesn't work for me: TZ=Europe/Moscow date --date='TZ="Asia/Taipei" 18:00' Mon Mar 27 18:00:00 CST 2017 -- i.e. it just tells me the date in Taipei, not my local date for that time point. Although manpage says your method is correct. Am I missing something?.. coreutils 8.26, Arch Linux

[exebook]

To find a timezone identifier use somethin like: timedatectl list-timezones|grep -i taipei (prints Asia/Taipei), timedatectl list-timezones|grep -i berlin (prints Europe/Berlin), timedatectl list-timezones|grep -i angeles (prints America/Los_Angeles)

[cesarpachon]

fantastic script! already added to my toolset, thanks! do you think it is possible to render time in columns instead of rows?

[Iuri Gavronski]

Maybe. I don't see a use for that, though.

[Ding-Yi Chen]

@MarSoft Check whether you have /usr/share/zoneinfo/Europe/Moscow

[Ben]

@Ding-YiChen yes, I do.

[jcdl]

For some reason this doesn't work with the version of date that ships with macOS. I've encountered similar issues before and use GNU coreutils. If you use Homebrew, do brew install coreutils, then use gdate (or gdd, etc.) then this answer works.

[Alex Reds]

@IuriGavronski interesting script. While playing around with it I noticed for the loop for hours goes beyond 24 hours range. It shows minus hours below 00 and goes beyond 24. e.g. Australia/Sydney Sydney 19 20 21 22 23 24 25 26 27 28 29 30 31 (+11).

[Alex Reds]

I assume the loop needs to be limited from 00 to 23. Then in the above example, it would be Sydney 19 20 21 22 23 00 01 02 03 04 05 06 07 (+11)

[Iuri Gavronski]

I never thought about that. I generally don't schedule meetings for those ungodly hours... 😉

[Iuri Gavronski]

Good observation. I don't mind, because the output is just for my own use, but that's a good suggestion.

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