That means the issue doesn't actually belong here! Ok. Despite that, will you suggest some ad hoc measures (like changing system time etc.) to get things going until we either shift to some other platform or find a solution?

This is a Linux or Java platform-level issue. Any Java program that executes on the same server should experience the same problem. You could write a simple Java program to verify this and maybe help with debugging the problem.

Also, check the timestamps of the events in your database and see if they match the JVM. If there is a skew between the database values and time in the JVM, you may get bad behavior in OpenNMS (missing events and collected data).