The current version of the CDISC TMF Reference Model is v3.3.1 (15Aug2023) and you can find it here. There is a major effort working on V4 which will become effective in 2027.
CDISC TMF Refence Model has two Date Convention Documents; one spreadsheet and one word document. Here is the link, then look for ‘TMF Resources’ at the bottom of the page, then ‘Date Conventions’