regression in cairo 1.17.4: invalid PDF date strings
(Follow-up from my comment to !35 (merged))
Cairo 1.17. introduced a bad/outdated date string format as it always append a single quote at the end which was not there previously. Likely culprit is commit e3415a31 (though I did not verify this).
I do not know anything about PDF internals but I found a StackOverflow question with relevant information. The "PDF 32000-1:2008" standard in section 7.9.4 ("dates") mandates that date strings use ( D : YYYYMMDDHHmmSSOHH' mm )
and according to StackOverflow the single quote at the end was only valid in a previous specification.
Background: proposed pull request for cairocffi.