What UTCTimeSynchronization Is
UTCTimeSynchronization is a remote-device-management service in BACnet, defined in Clause 16.8 of ANSI/ASHRAE 135-2024. It is the Universal Coordinated Time (UTC) counterpart to TimeSynchronization: a time master sends UTC so devices can compute their own local time from a time-zone offset and daylight-saving rules. It is an unconfirmed service and is usually broadcast.
UTC-based synchronization is the cleaner model for sites that cross time zones or need to survive daylight-saving transitions without every device being adjusted by hand.
How It Works
The time master sends the current UTC. Each receiving device applies its own configured UTC offset and daylight-saving setting to derive local time, then sets its clock. Because the wire value is UTC, a daylight-saving change is handled by each device’s local rules rather than by re-broadcasting a new local time. A device typically supports either this service or the local-time TimeSynchronization, matched to how its clock is modeled.
Where You’ll See It
- Multi-time-zone estates. A central time master feeding buildings in different zones, each deriving its own local time from the same UTC.
- Daylight-saving robustness. Devices roll their local time at the DST boundary from their own rules, with no re-broadcast needed.
- Consistent event ordering. UTC timestamps make cross-site event correlation unambiguous.
UTCTimeSynchronization Error Codes
UTCTimeSynchronization is an unconfirmed, usually broadcast service, so it has no acknowledgment and returns no application-layer error. When local clocks are wrong despite UTC sync, the causes are configuration, not protocol errors:
- A device’s UTC offset or daylight-saving setting is wrong, so it derives the wrong local time from correct UTC.
- Devices expect local-time TimeSynchronization instead of UTC, or vice versa.
- The broadcast does not cross subnets without a BACnet BBMD path.
Profiles That Require It
Accepting UTCTimeSynchronization comes from DM-UTC-B. The controller profiles that must keep an accurate clock, B-BC and B-AAC and the advanced life-safety, access-control, and elevator controllers, require either DM-UTC-B or the local-time equivalent DM-TS-B, not both. Sending time synchronization is the behavior of a time master.
What Chipkin Provides
The CAS BACnet Stack accepts UTCTimeSynchronization, applying the device’s offset and daylight-saving rules to set its clock. Talk to us about adding BACnet server support to your device.