Android - How do wi-fi only Android devices synchronise time?
We confirmed with the device manufacturer that the devices use NTP to sync the time with pool.ntp.org. After a bit of research of my own, I discovered that NTP is configured in
/system/etc/gps.conf. You have to be root to edit this file, but I was at least able to confirm that the information given to us was correct.
We have opened the firewall to traffic going to pool.ntp.org, and so far all of the devices have kept in sync, so it looks like this has worked as intended.
Thanks to http://forum.xda-developers.com/showthread.php?t=1200089 for the info on the NTP config file.
dotVezz has already commented that NTP is used.
If so, then you can use ClockSync, which lets you set the NTP server. HOWEVER, you need to sync manually. Automatic sync is supported only with ROOTED devices.
ClockSync synchronizes device system clock with atomic time from Internet via NTP (Network Time Protocol). Useful if provider doesn't support NITZ, sends incorrect time or if your device/ROM has heavy clock drift. There are 2 modes: automatic for root users and assisted manual mode for users without root (rootless mode).
You can DNS override the pool.ntp.org entry in your corporate DNS infrastructure, and make that an alias/CNAME to your own internal NTP source/service. That will allow the internally connected android devices to sync with NTP without modification of the device itself