MIKES time and frequency laboratory is the national measurement standard laboratory for time interval and frequency and maintains the official time in Finland. Of all quantities frequency can be measured most accurately. MIKES Cs atomic clocks and hydrogen masers frequency can be realised with a relative uncertainty of 3·10-13. In time, this corresponds to an error of one second in 100 000 years. The time of day is determined with an uncertainty of 0.02 µs by using GPS satellite receivers in common-view mode and is reported as coordinated universal time (UTC) according to international time standard. MIKES time laboratory maintains a NTP service that can be used to synchronise computers via internet to the Finnish official time. The national measurement standard laboratory for time and frequency maintains a normal frequency transmitter, also.