Are you using AX 3.4 or later? The time protocol that uses UDP port 37 has been superseded by NTP, which typically uses TCP port 123.
Some of NIST's servers still answer on port 37, for how long, I don't know.
The server time.nist.gov no longer responds to requests for time in the TIME format (as defined in RFC-868). These requests are generated by a number of different programs including DATE, RDATE, and other programs that connect to the time server using tcp or udp port 37. All of the other NIST servers (except for time-nw.nist.gov) will continue to respond to requests to either tcp or udp port 37 for time in the format specified in RFC-868.
However, this format has poor error-handling capabilities in general, and many of the client programs that use this format are poorly written and may not handle network errors properly. Therefore users are strongly encouraged to switch to the Network Time Protocol (NTP), which is more robust and provides greater accuracy. We eventually intend to phase out support for the TIME format on all servers.
Tridium's timesync service does implement some error-handling sanity checks, but if you are running 3.4 or later, I would switch to NTP.
Do you have a PC based station, or only embedded Jaces?
If you have a PC based station then in any build you can use Windows time service to NTP sync to a NTP time server on the LAN or internet. In the Niagara station on the PC you can setup the older timesync service and make the station an RFC-868 time server. Then configure the Jaces to sync to the PC station.
Not everything that can be counted counts, and not every thing that counts can be counted - Albert Einstein