Another explication with (JS) code of the MS-DOS datetime encoding is at https://github.com/PaulCapron/pwa2uwp/blob/79ae42ea43e98eaf9...

https://github.com/PaulCapron/pwa2uwp/blob/master/src/zip.js in its entirety provides a simple intro, with code, to the ZIP format (archiving only, with no compression)