Convert creation/modification dates to UTC (fixes #155)

phmccarty commented

2023-05-29 21:20:07 +00:00

Contributor

(Tested with Python 3.11.3 on Arch Linux.)

Ensure that timezones are correctly interpreted in the input by calling
.astimezone() as appropriate on datetime objects, and store the
resulting date fields as UTC.

One could argue that datetimes in the local timezone be stored in the
PDF, but then the date string handling becomes more complicated; the PDF
and XMP date specs both use the Z suffix to indicate UTC time, but
other +/- offsets require different syntax between the two specs.

(Tested with Python 3.11.3 on Arch Linux.) Ensure that timezones are correctly interpreted in the input by calling `.astimezone()` as appropriate on datetime objects, and store the resulting date fields as UTC. One could argue that datetimes in the local timezone be stored in the PDF, but then the date string handling becomes more complicated; the PDF and XMP date specs both use the `Z` suffix to indicate UTC time, but other +/- offsets require different syntax between the two specs.

phmccarty added 1 commit 2023-05-29 21:20:09 +00:00

Treat default creation/mod dates as UTC (fixes #155 ) 1dd05cc36b

(Tested with Python 3.11.3 on Arch Linux.)

Without passing a tzinfo object to `datetime.now()`, a "naive" datetime
object is created, which is not timezone-aware. To fix the default
date/time detection for non-UTC local timezones, pass
`datetime.timezone.utc` to convert the value to UTC and make the
datetime object "aware".

Also, adjust the strftime() wrappers to use the UTC offsets instead of a
literal `Z`; using the literal `Z` at the end appears to be valid for
ISO 8601, but for some reason it does not successfully convert, whereas
the `%z` placeholder substitutes the UTC offset and successfully
converts.

phmccarty commented

2023-05-30 00:29:47 +00:00

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Contributor

After doing a bit more research, I discovered that PDF and XMP have different syntax for timezone offsets... I pushed an experimental change to another branch (atop this branch): https://gitlab.mister-muffin.de/phmccarty/img2pdf/commits/branch/pdf-xmp-timestamps

phmccarty added 2 commits 2023-06-11 00:35:14 +00:00

Convert manual creation/mod times to UTC as well 9c3753ed2b

In line with the previous commit for consistency, convert the date
strings from --creationdate and --moddate to UTC as well if a timezone
is specified.

Fix format of PDF and XMP timezone offsets 85efd9a80a

The way to specify timezone offsets differs between the PDF and XMP
specs, so hardcode the UTC offset instead of using `%z`. This also
avoids the possibility of embedding the more more granular timezones
supported by the datetime module but that are unsupported by either PDF
or XMP formats.

phmccarty commented

2023-06-11 00:35:51 +00:00

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Contributor

Updated the MR to reflect the discussion from #155

phmccarty force-pushed utc-timestamps from 85efd9a80a to 512478ac4e

2023-06-11 00:37:01 +00:00

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phmccarty changed title from ~~Treat default creation/mod dates as UTC (fixes #155)~~ to Convert creation/modification dates to UTC (fixes #155)

2023-06-11 00:43:23 +00:00

phmccarty force-pushed utc-timestamps from 512478ac4e to 81502f21af

2023-06-11 01:01:49 +00:00

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phmccarty commented

2023-06-11 01:05:17 +00:00

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Contributor

One more update: I squashed changes into one commit to minimize the churn between commits.

josch merged commit 81502f21af into main

2023-06-11 05:30:53 +00:00

phmccarty deleted branch utc-timestamps

2023-06-11 07:14:48 +00:00

Convert creation/modification dates to UTC (fixes #155) #168