All times in OPC UA are in UTC, however, UTC can include discontinuities due to leap seconds or repeating seconds added to deal with variations in the earth’s orbit and rotation. Serversthat have access to source for International Atomic Time (TAI) may choose to use this instead of UTC. That said, Clientsshall always be prepared to deal with discontinuities due to the UTC or simply because the system clock is adjusted on the Servermachine.