You don't understand the startdates?
Take, for example, 20190521.2300
Let me stick some spaces in some helpful places:
2019 05 21 . 23 00
That better?
20190521 means 21st May 2019, and 2300 is in 24-hour clock format, IE 11:00PM
Stardates in the Star Trek universe work in an entirely different way. Wikipedia has a good explanation on how Stardates work.