You don't understand the startdates?
Take, for example, 20210426.0000
Let me stick some spaces in some helpful places:
2021 04 26 . 00 00
That better?
20210426 means 26th April 2021, and 0000 is in 24-hour clock format, IE 12:00 midnight
Stardates in the Star Trek universe work in an entirely different way. Wikipedia has a good explanation on how Stardates work.