Re: Convert UTC time to local time using strftime and zsh/datetime

[Kurtis Rader <krader@skepticism.us>]

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If you believe the formatted date/time string is in the UTC timezone you
need to

TZ=UTC strftime -r "%Y-%m-%d %H:%M:%S +0000" "2015-02-11 16:42:30 +0000"

Which should yield 1423672950 as the seconds since the UNIX epoch.

I use the following Python program to convert seconds since the UNIX epoch
to UTC and local time. For example (note that I'm on the west coast of the
USA, UTC-8):

$ time2str 1423672950
UTC   2015-02-11 16:42:30
Local 2015-02-11 08:42:30



#!/usr/bin/env python2.7
from __future__ import print_function

import sys
import time

TIME_FMT = '%Y-%m-%d %H:%M:%S'

seconds_epoch = float(sys.argv[1])
utc = time.gmtime(seconds_epoch)
local = time.localtime(seconds_epoch)

print('UTC   {}'.format(time.strftime(TIME_FMT, utc)))
print('Local {}'.format(time.strftime(TIME_FMT, local)))



On Fri, Feb 20, 2015 at 8:41 PM, TJ Luoma <luomat@gmail.com> wrote:

> I have a screenshot of my iPhone which shows that it was taken at 11:42
> a.m.
>
> When I look at the file in Finder, it shows that it was taken at 11:42 a.m.
> on Feb 11
>
> You can see a screenshot here:
> http://images.luo.ma/skitch/iPhonePhotos-1142am-20150220-231455.jpg
>
> When I use `mdls -raw -name kMDItemContentCreationDate test.png` (a Mac
> command to get the Creation Date), I get
>
> 2015-02-11 16:42:30 +0000
>
> as the answer. This is, I believe, UTC. So I need to convert that to local
> (US/Eastern) time.
>
> I'm not sure how to do that, so heres what I did
>
> 1) Load the appropriate module
>
> > zmodload zsh/datetime
>
> 2) get the Unix EPOCH time from the date/time stamp we have:
>
> > strftime -r "%Y-%m-%d %H:%M:%S +0000" "2015-02-11 16:42:30 +0000"
> 1423690950
>
> 3) Convert '1423690950' to US/Eastern time:
>
> > strftime "%Y-%m-%d %H:%M:%S" "1423690950"
> 2015-02-11 16:42:30
>
> But that's still giving me '16' as the hour. It should be 11, shouldn't it?
>
> 4) Try again, this time making sure that I define the time zone:
>
> > TZ=US/Eastern strftime "%Y-%m-%d %H:%M:%S" "1423690950"
> 2015-02-11 16:42:30
>
> Same time.
>
> OK, so I'm obviously missing something. I checked '1423690950' on various
> online "Unix time" converters and they confirm that it's 16:42 my time, but
> since I know the picture was taken at 11:42, I'm wondering what I did
> wrong.
>
> Tj
>



-- 
Kurtis Rader
Caretaker of the exceptional canines Junior and Hank