You don't understand the startdates?
Take, for example, 20190528.1900
Let me stick some spaces in some helpful places:
2019 05 28 . 19 00
That better?
20190528 means 28th May 2019, and 1900 is in 24-hour clock format, IE 7:00PM
Stardates in the Star Trek universe work in an entirely different way. Wikipedia has a good explanation on how Stardates work.