Kind of puzzled about timestamps

Thu Mar 4 20:49:06 EST 2021

Weird, it is just the 5 hours between UT and EST.  The files are 
generated on a non-linux embedded machine.
If I create a file on my pc, then the TZ information is present and the 
time is set.  ls reads it correctly.

This time stuff can get confusing.  As you were.

On 3/4/21 7:13 PM, Bruce Labitt wrote:
> Good point.  I'll check that.  Logging machine was set to local time 
> EST.  But it does have a wireless link, maybe it set itself internally 
> to UT.  Thanks for the hint.
>
>
>
> On Thu, Mar 4, 2021, 7:05 PM Dana Nowell 
> <dananowell at cornerstonesoftware.com 
> <mailto:dananowell at cornerstonesoftware.com>> wrote:
>
>     If I'm reading it correctly, it's a 5 hr difference?  Local vs gmt?
>
>
>     On Thu, Mar 4, 2021, 6:43 PM Bruce Labitt
>     <bruce.labitt at myfairpoint.net
>     <mailto:bruce.labitt at myfairpoint.net>> wrote:
>
>         This is an odd question.  It involves both python and linux.
>
>         Have a bunch of files in a directory that I'd like like to
>         sort by similar names and in time order.  This isn't
>         particularly difficult in python.  What is puzzling me is the
>         modified timestamp returned by python doesn't match whats
>         reported by the file manager nautilus or even ls.  (ls and
>         nautilus are consistent)
>
>         $ lsb_release -d Ubuntu 20.04.2 LTS
>         $ nautilus --version  GNOME nautilus 3.36.3
>
>         $ python3 --version  Python 3.8.5
>
>         $ ls -lght
>
>         total 4.7M
>         -rw-r--r-- 1 bruce 209K Feb 26 01:49 20210226_022134_PLD.edf
>         -rw-r--r-- 1 bruce  65K Feb 26 01:49 20210226_022134_SAD.edf
>         -rw-r--r-- 1 bruce 2.4M Feb 26 01:49 20210226_022133_BRP.edf
>         -rw-r--r-- 1 bruce 1.1K Feb 26 00:58 20210225_224134_EVE.edf
>         -rw-r--r-- 1 bruce 1.9M Feb 25 21:18 20210225_224141_BRP.edf
>         -rw-r--r-- 1 bruce 169K Feb 25 21:17 20210225_224142_PLD.edf
>         -rw-r--r-- 1 bruce  53K Feb 25 21:17 20210225_224142_SAD.edf
>
>         Python3 script
>
>         #!/usr/bin/env python3
>         import os
>         from datetime import datetime
>
>         def convert_date(timestamp):
>           d = datetime.utcfromtimestamp(timestamp)
>           formatted_date = d.strftime('%d %b %Y  %H:%M:%S')
>           return formatted_date
>
>         with os.scandir('feb262021') as entries:
>           for entry in entries:
>             if entry.is_file():
>               info = entry.stat()
>               print(f'{entry.name <http://entry.name>}\t Last
>         Modified: {convert_date(info.st_mtime) }' )  # last modification
>
>         info /(after exit) contains/: os.stat_result(st_mode=33188,
>         st_ino=34477637, st_dev=66306, st_nlink=1, st_uid=1000,
>         st_gid=1000, st_size=213416, st_atime=1614379184,
>         st_mtime=1614322176, st_ctime=1614379184)
>
>         Running the script results in:
>
>         20210226_022133_BRP.edf  Last Modified: 26 Feb 2021  06:49:34
>         20210225_224141_BRP.edf     Last Modified: 26 Feb 2021  02:18:42
>         20210225_224142_PLD.edf     Last Modified: 26 Feb 2021  02:17:44
>         20210225_224142_SAD.edf     Last Modified: 26 Feb 2021  02:17:44
>         20210225_224134_EVE.edf     Last Modified: 26 Feb 2021  05:58:26
>         20210226_022134_SAD.edf     Last Modified: 26 Feb 2021  06:49:36
>         20210226_022134_PLD.edf     Last Modified: 26 Feb 2021  06:49:36
>
>         Actually, what is returned by my script is at least sensible,
>         given that 20210225_224141_BRP.edf started on Feb 25th and
>         ended recording at 2:17am on Feb 26th.  I know this because I
>         can see the data on a separate program.
>         20210226_022133_BRP.edf started on Feb 26th at around 2:21am
>         and terminated at 6:49am.  BRP files are written to
>         continuously at a 25 Hz rate all evening.  What makes no sense
>         whatsoever is what *ls* is reporting.
>
>         Do *ls* and python3 use different definitions of "last modified"?
>
>         Guess I can keep going, but I really was surprised at the
>         difference between methods.  Default for ls is "last
>         modified", at least as reported by man.  ls's last modified
>         just isn't correct, at least on Ubuntu 20.04.2
>
>         Is this a quirk?  Am I doing something wrong?  Some kind of
>         voodoo definition of "last modified"?  What does Linux say
>         "last modified" really means?
>
>         FWIW, I am coming up to speed on processing these edf files to
>         help out on an open source project.  Been working on some data
>         analysis tools.  As an aside, biological data is very messy. 
>         It's been a treat to work on this as it's forced me to dust
>         off the mental cobwebs and work on a problem that can help a
>         lot of people.
>
>
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