I quickly tried using exact same structure as you mentioned in version 8.8.0 (same as yours) but don't find any issues. LastLogin is displayed in expected data format. Its strange you are having this issue, is the user accessing the page got correct access on Employee and party entity? LastLogin can only be accessed by administrator role.
the last login attribute is on read only, even as an admin, you can check the entity of system user.
The only way to do it is for you to find a way to put it in the admnistration account. and to see it from there.
if you want to do like that, you can do as i did here (see my answer): https://forum.mendix.com/link/questions/100132
I logged in as adminsitrator and checked the same page / view – it is displayed correctly.
And: when I switch to standard Date & Time (as opposed to custom), it is the same phenomenon.
It is not an MM / mm issue or anything….
I will take the LONG numbers now and manually translate them into a date/time.
In case that works, it is a major permission issue: It would not be displayed at all or fully (including a proper format translation)
So I checked the permissions by assigning the App role I am using to be the System module administrator (instead of user): Rendering works!!
I also took the “long” number and translated it into dates and they are real date/time combinations.
This looks like a very serious bug!