We recently had an odd issue where the virtual machine running NetXMS crashed and came up with the time 4 days in the future. While we fixed that, I found that NetXMS does not cope with such an issue in that it stops polling node status and DCIs as the last poll now was four days in the future. The Last Value field also showed as completely empty and even with debugging I could not see why it would not poll at all.
I got this working again by going through the database and updating/deleting entries with such timestamps (e.g. updating the nodes table, deleting data from idata and raw_dci_values and a few other tables).

The feature request would be to have nxdbmgr check for invalid/future timestamps and allow them to be fixed in a safe way.
Polls in the future should probably be deleted as it's impossible to tell when they were really polled, while the timestamps for node down since or last poll could be reset to "now"?

I admit that this shouldn't happen to begin with. But when it does, it can be quite a pain to resolve.

Thanks.