Dordrecht, did your admins change the TIME on the server, or the server's time ZONE setting? The latter would make sense, since most systems now rely on an internet time server to know the time. But often their timezone is off and may need to be changed.
If they did change only the system's time ZONE, then what happened makes more sense. Let me explain.
To be clear, this is not about cf but the jvm on which cf runs. It defaults to using the system timezone on start, unless (as John noted) you DID set the timezone in Java, but you clarify that you did not.
But the issue here is that the jvm does NOT auto-detect your changing the os time ZONE once the jvm (cf) running. (It WOULD have detected if you'd changed the server TIME, but you did not, right? just the timezone?)
And so yes, resarting only cf would have fixed things, as did the box reboot.
Finally, as for your not finding more on this on the web, that may be so if you searched relative to cf. But if you search relative to java instead, a first result could have been this SO exchange (about the same issue in Tomcat), where one guy addresses the point in excessive detail (which is saying something, coming from me!):
https://stackoverflow.com/a/49121103
Hope my clarification helps.