My temporary solution was to disable the rate limiting feature in my NTP server (sometimes its labeled as 'KOD packet', the NTP kiss of death packet). You may also try using a public NTP server that does not rate limit. Do you happen to be in GMT-8? That would explain the 8 hours off.
I've found that my dahua cameras also incorrectly implement the NTP protocol. There are 2 issues:
1) It sends localtime instead of UTC time in the ntp.xmt field
2) It sends multiple requests right after one another (1ms apart) in bursts up to 3
Some NTP servers throttle the number of requests...