If you can run a UDP traceroute to port 123 on one of the time servers that you're using, that should give you an indication of where the firewall is located.
Net Time is syncing, but the time is out by an hour - e.g.
Daylight savings time isn't be honoured correctly: Net Time works internally with UTC (Universal Time) and doesn't have any code for handling daylight savings or time zones.
I've experienced this issue several times, personally, and it always makes me wish Android's clock would simply sync with official time-keeping services like NTP or NIST.
Well thanks to a recent update to a popular Android app, this can finally be accomplished on newer Android versions, meaning you can ensure that your system clock is always in sync with atomic time.
If you uninstall the old version first, you will need to restart your computer before starting the new installer.
Net Time is failing to sync - it reports that all servers failed: The most common cause of this error is that a firewall is blocking the Network Time Protocol (UDP Port 123) between your system and the servers that Net Time is attempting to use.
For most Android phones, the system clock is set using a protocol called NITZ, which relies on a connection with your carrier to ensure that the time stays in sync.
The trouble here is that this feature won't work when you're outside of cellular range, and a lot of times, the carriers themselves have technical difficulties that can result in your phone's clock being minutes or even hours out of sync.
Always provide time: Enabling this option isn't recommended.