macOS Preview App Displays Incorrect Date/Time due to Timezone Formatting

[appare45]

I've encountered a rendering issue where the macOS Preview app seems to ignore the timezone offset specified in the CreationDate and ModDate fields.

This appears to be a compatibility issue with Preview, as other viewers like Adobe Reader display the date and time correctly.

Environment

• pdf-writer: 0.14.0
• macOS: Sequoia 15.6.1
• Preview.app: Version 11.0 (1069.7.1)

Steps to Reproduce

1. Generate a PDF file with a specific date and UTC offset. My system's timezone is JST (+09:00).

   let date = Date::new(2025)
           .month(10)
           .day(13)
           .hour(17)
           .minute(0)
           .second(0)
           .utc_offset_hour(9);
   pdf.document_info(document_info_id)
       .modified_date(date)
       .creation_date(date);

2. Open the resulting PDF file with the macOS Preview app.

Observed Behavior

Preview displays the time as 02:00, seemingly ignoring the +09:00 offset and falling back to UTC.

Expected Behavior

The time should be displayed as 17:00, correctly reflecting the provided timezone offset. For comparison, Adobe Reader renders it correctly.

Proposed Solution

After inspecting the raw PDF output, I found that adding a trailing apostrophe (') to the date string's timezone offset resolves the issue in Preview.

Before (Current pdf-writer Output):

$ strings target/before.pdf | grep Date
  /ModDate (D:20251013170000+09'00)
  /CreationDate (D:20251013170000+09'00)

After (With Proposed Fix):

$ strings target/after.pdf | grep Date
  /ModDate (D:20251013170000+09'00')
  /CreationDate (D:20251013170000+09'00')

This format with the trailing apostrophe appears to be a common practice for ensuring compatibility. For instance, a PDF generated by Microsoft Word uses the same format for its date strings, as shown below:

$ strings MS_WORD.pdf | grep "/CreationDate"
/Creator(Microsoft Word) /CreationDate(D:20251013090356+00'00') /ModDate(D:20251013090356+00'00')

Applying the following diff to pdf-writer would align it with this practice and fix the parsing issue in macOS Preview.

diff --git a/src/object.rs b/src/object.rs
index 99e8ca6..bdfa338 100644
--- a/src/object.rs
+++ b/src/object.rs
@@ -557,7 +557,7 @@ impl Primitive for Date {
                 } else {
                         write!(
                                 buf.inner,
-                                "{:+03}'{:02}",
+                                "{:+03}'{:02}'",
                                 utc_offset_hour, self.utc_offset_minute
                         )
                         .unwrap();

Would you consider applying this change to improve compatibility with the macOS Preview app?

If you do not plan to address this, please feel free to close this issue. Thank you for your consideration!

[laurmaedje]

The PDF 1.7 spec Section 7.9.4 has no mention of a trailing apostrophe being legal. Do you have any source that this is even valid PDF?

[appare45]

Yes, the PDF 1.7 specification's text on date formatting doesn't explicitly mention a trailing apostrophe. However, the example shown in section 14.3.3 does include one.

1 0 obj
<< /Title ( PostScript Language Reference, Third Edition )
/Author ( Adobe Systems Incorporated )
/Creator ( Adobe FrameMaker 5 . 5 . 3 for Power Macintosh® )
/Producer ( Acrobat Distiller 3 . 01 for Power Macintosh )
/CreationDate ( D : 19970915110347 - 08 ' 00 ' )
/ModDate ( D : 19990209153925 - 08 ' 00 ' )

https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf#page=558

[laurmaedje]

That's odd. But honestly I'm not comfortable with writing output that does not match what the description in the spec says because of some later example. It could easily create compatibility problems with software that simply parses the date as written in the spec. Preview unfortunately has a lot of bugs ...

[LaurenzV]

Might be worth asking in https://github.com/pdf-association/pdf-issues/issues.

[appare45]

I've read the PDF 2.0 spec (ISO 32000-2:2020) got from PDF association and found out the following note. This note may confirm that adding the trailing apostrophe is the correct approach for ensuring backward compatibility.

PDF versions up to and including 1.7 defined a date string to include a terminating apostrophe.
PDF processors are recommended to accept date strings that still follow that convention.

[laurmaedje]

It seems like the Adobe PDF 1.7 spec wants the terminating apostrophe, but the ISO 32000-1:2008 PDF 1.7 spec not. PDF specs up to 1.6 from Adobe also contain it. As neither of the specs mention the apostrophe being optional, this seems like a breaking change in the ISO version of PDF to me, which I find odd.

The note in the PDF 2.0 spec refers to PDF processors accepting such date strings, which I do not think implies that PDF writers should write it, or else the whole change would be pointless. For PDF 2.0, I would thus definitely not write it. For PDF 1.7 it makes more sense (not sure) and for 1.6 and below, we should definitely write the apostrophe. This implies that pdf-writer needs version configuration ...

cc @reknih

[reknih]

Reference link for a pre-ISO 1.7 spec: https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/pdfreference1.7old.pdf
Post-ISO spec for 1.7 missing the apostrophe: https://opensource.adobe.com/dc-acrobat-sdk-docs/pdfstandards/PDF32000_2008.pdf

[reknih]

The plot thickens: There is an Adobe erratum for the Pre-ISO 1.7 spec (archived link of https://www.adobe.com/devnet/pdf/pdfs/pdf_17_errata.pdf). In it, the sentence...

The apostrophe character ( ' ) after HH and mm is part of the syntax.

...is removed without replacement. The paragraph is reworded to its ISO form. What is not reworded, is the ASCII summary and the list above. I am not sure whether the intent of this erratum is to clarify the syntax or to remove the trailing apostrophe. In the first case, I'd argue the current behavior for PDF 1.7 and 2.0 is okay and only PDF 1.6 and earlier should get the apostrophe, otherwise, I'd go with what's codified in the earliest available PDF 1.7 spec (so write the apostrophe for PDF 1.7 and earlier).