Nagios Support Forum

I had these problems too, but I don't know the specific solution I used for it.
One of the solutions was to edit the PHP time, but you already done this. The other solution had to do with the fact that the checks were entered before the time/date change and I had to add the hosts and services again. This was no problem with our situation as it was an evaluation server which was barely configured. Your case might be different, but to check this, I would recomend adding a new host with some general checks and see if the time is correct now.
You may also want to try a restart of the nagios service (accept configuration in CCM)

If this keeps happening after restarting I also would have to wonder if somehow the system is getting populated with a bas date from the vmware server or something.