Re: [tlug] Ubuntu 13.10 clock problems (was: Ibus and Ubuntu based)

[Bruno Raoult <braoult@example.com>]

On Sat, Nov 9, 2013 at 5:22 PM, Lyle H Saxon <llletters@example.com> wrote:

> Could you send us the metadata of one file on the SD card and on your Linux
> box after the copy? I mean as shown by the Linux box.
> You can get it with the command "exiftool" (or others, there are many).

I also thought that would be impossible, but after a few batches, I
noticed a wrong date, and when I checked the different batches, it
correlated with using that Live-DVD to perform that task, and when I
tried it again, that was the result.

In fact, I am not sure of what you call "meta-data" and "wrong date".

I could understand the "file date" could be changed or wrong.

But *picture* meta-data (creation date) has nothing to do with the copied *file* creation date.

After copy, they could (should?) differ.

What I don't know is how you did check the date on Linux system: Was it the *file* time (in filesystem) or the picture ("date taken"), available in .jpeg EXIF data? And how the Linux system did see the SD card files times?

I suggest you use "exiftool" to get the picture meta-data, so we can forget about the timezone issue itself, and focus on clock problem.

To be concise: I believe pics meta-data was not changed. There could be an issue with file systems times (creation and/or modification time). I guess your SD card was in localtime, Japan time (I mean when pictures were taken). How about the Linux machine? UTC or localtime?

Please check the "mount" man page. You can read:

tz=UTC This option disables the conversion of timestamps between local time (as used by Windows on FAT) and UTC (which Linux uses internally).  This is particularly useful when mounting devices (like digital cameras) that are set to  UTC in order to avoid the pitfalls of local time.

Could it be this kind of issue? If yes, I don't know what to say. By definition, FAT

filesystems don't have timezone understanding. What should assume a Linux box when mounting such a filesystem?

If I check one of my pictures (with exiftool), I get:
br@lorien$ exiftool p1020419.jpg | grep '\(Date\|Time\)'
File Modification Date/Time     : 2010:04:14 04:55:24+02:00
File Access Date/Time           : 2013:11:10 21:55:24+01:00
File Inode Change Date/Time     : 2013:04:06 10:03:30+02:00
Modify Date                     : 2010:04:14 03:55:25
Exposure Time                   : 1/30
Date/Time Original              : 2010:04:14 03:55:25
Create Date                     : 2010:04:14 03:55:25
Time Since Power On             : 00:00:21.73
Self Timer                      : Off
World Time Location             : Home

The 3 first lines are filesystem related. All the others are pic metadata. Obviously file dates were modified. If I edit the picture, "Modify Date" should change too, if my editing program manages it. However, the "Create Date" or "Date/Time Original" (not sure which one) should never change. And they are the *real* dates when picture was taken (the time the camera had at that moment). Other times (FS related) are meaningless.

If (as I believe) your issue is file-system time related, exiftool allows to change filesystem's file dates and times according to EXIF data. For instance:
$ exiftool '-DateTimeOriginal>FileModifyDate' dir
  Use the original date from the meta information to set
  the same file's filesystem modification date for all images
  in a directory.

Would this help?

FYI, my newer camera (DMC-TZ10) has GPS builtin, and the output would be (including GPS information) something like:
br@lorien$ exiftool p1000369.jpg | grep '\(Date\|Time\|GPS\)'
File Modification Date/Time     : 2011:04:24 16:50:22+02:00
File Access Date/Time           : 2013:11:10 21:45:06+01:00
File Inode Change Date/Time     : 2013:04:06 10:10:44+02:00
Modify Date                     : 2011:04:24 15:50:23
Exposure Time                   : 1/25
Date/Time Original              : 2011:04:24 15:50:23
Create Date                     : 2011:04:24 15:50:23
Time Since Power On             : 00:06:01.10
Self Timer                      : Off
World Time Location             : Destination
GPS Version ID                  : 2.2.0.0
GPS Latitude Ref                : North
GPS Longitude Ref               : East
GPS Time Stamp                  : 08:49:33
GPS Satellites                  : 4
GPS Status                      : Measurement Active
GPS Measure Mode                : 2-Dimensional Measurement
GPS Dilution Of Precision       : 4.8
GPS Map Datum                   : WGS-84
GPS Processing Method           : GPS
GPS Date Stamp                  : 2011:04:24
GPS Date/Time                   : 2011:04:24 08:49:33Z
GPS Latitude                    : 7 deg 53' 40.89" N
GPS Longitude                   : 98 deg 17' 47.11" E
GPS Position                    : 7 deg 53' 40.89" N, 98 deg 17' 47.11" E

Here, my camera timezone was 7 hour ahead of UTC time and its time was wrong by 50 seconds (if we exclude GPS deviation, currently 16 secs ahead of UTC). Only GPS time allows pictures to have correct timestamps when you travel. Another issue with localtime :-)

As of my pictures management, I try to have the filesystem timestamp correct (all with same reference, UTC), and filename showing localtime where/when the pic was taken. Not ideal, but I did not find a better solution to have a correct order as well as "local" timestamp.

br.

--
2 + 2 = 5, for very large values of 2.