Sync cameras, recorders and door controllers to NTP the way NIST asks: no hard-coded servers and no fast polling

NIST operates stratum-1 time servers linked to UTC(NIST) and asks users to reach them through the round-robin name time.nist.gov, never hard-code one server name or address into a device, and never query more than once every 4 seconds. It strongly encourages moving from the old TIME and DAYTIME protocols to NTP.

Source facts

NIST’s Internet Time Service page says NIST operates several stratum-1 network time servers whose time is directly linked to UTC(NIST), the official NIST time, and that other sources of time are not monitored or certified by NIST. It says most operating systems can automatically synchronize their clocks periodically by querying an NTP server.

NIST’s time server list says the global name time.nist.gov resolves to all of its servers in a round-robin sequence to equalize load, that it is bad practice to hard-code a particular server name or address into a device so it cannot be changed later, and that software must never query a server more often than once every 4 seconds, with faster systems refused service. It strongly encourages users of the TIME protocol on TCP port 37 and the DAYTIME protocol on TCP port 13 to upgrade to NTP, and lists separate servers that answer only authenticated NTP requests from registered users.

NIST also says its servers add a leap second by repeating 23:59:59, which makes time tags in that second ambiguous and can make it difficult to establish the order of events near a leap second.

Applicability

Use this for any system whose logs or recordings may need to be correlated or used as evidence. Device time settings vary by manufacturer; confirm each device’s NTP options and time zone handling.

DSE recommendation

DSE recommends syncing every security device to an internal NTP source that is itself synced to a trusted reference, so video, access and alarm logs agree to the second. Configure time servers by name where devices allow it, keep polling intervals well above NIST’s 4-second floor, block the old TIME and DAYTIME protocols at the firewall, and alert on devices that drift.

Verification

Each quarter, compare timestamps from a camera, recorder, door controller and server against the reference clock, record any offset, and correct devices that drift beyond the tolerance set for investigations.

Official references

NIST — Internet Time Service (ITS). NIST — Internet Time Servers. Reviewed October 19, 2026.