How do wi-fi only Android devices synchronise time? I'm having a problem with some Android tablets being unable to synchronise the time when connected to our wireless network. This is in a school and fairly heavily locked down, so it's probable that they are being blocked from accessing something that they need to in order to synchronise the time.

These are Wi-Fi only devices, so they can't set the time from a GSM provider or anything, meaning they must be using something else, presumably NTP. If it's NTP, how can I view/change the time server used?

The devices are Android 4.0.1. I'm not sure what make/model they are but will try and find out.
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.