Looking for Help on Date Acceptance patterns, I found that ok, under Global - Languages, on file:///C:/Program%20Files/LibreOffice/help/en-GB/text/shared/optionen/01140000.html?DbPAR=SHARED#bm_id3154751 . On attempting to follow the link in "For all patterns, two-digit year input is interpreted according to the setting in Tools - Options - General - Year (Two Digits)" (last paragraph), which leads to file:///C:/Program%20Files/LibreOffice/help/en-GB/html?&DbPAR=SHARED&System=WIN#jahreszahlen , I get a 'Problem Loading Page' error, with: File not found Firefox can’t find the file at /C:/Program Files/LibreOffice/help/en-GB/html?&DbPAR=SHARED&System=WIN#jahreszahlen.
Olivier Hallot committed a patch related to this issue. It has been pushed to "master": https://git.libreoffice.org/help/commit/fd6e7ec2b20e751a092a38cc3c3c92acf82fde81 tdf#149607 Fix broken link
Olivier Hallot committed a patch related to this issue. It has been pushed to "libreoffice-7-4": https://git.libreoffice.org/help/commit/f4c7ca187f07329eff29ea3f7b9e3ed60b30a784 tdf#149607 Fix broken link
Done; can’t cherry-pick this one to the 7.3 branch due to the string freeze.