This seems to only happen on my newer builds using Ubuntu. I used to standardize on CentOS but have since made the switch to Ubuntu.
Running Ubuntu Server 9.04 amd64 (seeing this on 32bit boxes also)
Zoneminder built according to this guide:
http://www.zoneminder.com/forums/viewtopic.php?t=14281
I noticed that normando and cordel were troubleshooting this at the beginning of the year in 1.23.x:
http://www.zoneminder.com/forums/viewto ... light=1969
zmf is disabled and this is still happening.
Like normando, I verified that these timestamps are being written to the database with the 1969 timestamp.
I have not configured any php TZ yet.
Can anybody point me in the right direction?

