Safe Time Source

Service dedicated to Time Stamping Units


As a reliable source of time, the time provided by one of the laboratories recognized by the international public body Bureau International des Poids et Mesures (BIPM). 


BIPM publishes monthly through its website ( the list of the set of large atomic clocks in the national metrology institutes and the national astronomical observatories that cover the whole planet.


The International Atomic Time (TAI) is calculated by Bureau International des Poids et Mesures (BIPM), reading a network of 200 atomic clocks located in institutes laboratories and metrology observatories spread over more than 30 countries worldwide. ROA is an integral part of the network described.


The laboratory selected by ANF AC TSA is the Royal Institute and Observatory of the Navy - San Fernando (Cádiz), “ROA”. 


Declared for legal purposes as the National Patron of this unit, as well as for the maintenance and official dissemination of the scale "Universal Coordinated Time" (UTC (ROA)), considered for all purposes as the basis of legal time throughout the national territory (RD October 23rd, 1992, No. 1308/1992).


This lab maintains several servers that distribute the time via RedIRIS through the NTP protocol. This system of high stability and precision allows to know the UTC time (defined in ITU-RTF.460-6) with a precision superior to the microsecond, and with a stability of 32 s / year 5.

The SS-ROA consists mainly of a Rubidium frequency pattern (Symmetricom Rubidium Frequency Standard 8040), a system of time and frequency comparison using GPS satellite navigation system (GPS Symmetricom SyncServer S200 and Dicom Time & Frequency Transfer RE-Giver) and two External Synchronization Centers mod. STF701. 


The set of these equipment produces a series of files that contain the data of the follow-ups carried out in a day, which are used by the ROA to elaborate the difference phase reports of the standard with the scale UTC (ROA). 


The UTC date and time reference is supplied to the network via the STF701 External Synchronization Centers, through a NTP service (Stratum 0).


The UTC system uses the Greenwich Mean Time, ignoring the DST movements. Since January 1, 1972, UTC is the international time standard, and while Coordinated Universal Time (UTC) has replaced "Greenwich Mean Time" (GMT), in practice there is never more than 1 second of difference.


The UTC time scale, based on the second, is defined and recommended by the International Telecommunications Union Radio (ITU-R) Recommendation TF.460-4.


UTC time zero (0) is midnight in Greenwich, England, where the longitudinal meridian is at zero. Universal time is based on 24 hours, therefore, clock hours such as 4 pm in UTC are expressed as 16:00 UTC (sixteen hours, zero minutes).


The level of operation is Stratum I, because the server gets its time signals from a dedicated hardware device, that is synchronized with the UTC (Coordinated Universal Time) scale with an accuracy within the microsecond.


The Stratum I NTP Server consists of an IP packet transmitter with time information about the current universal time value UTC through the Network Time Protocol (NTP). The level of operation is Stratum I because the server gets its time signals from a dedicated hardware device that is synchronized with the UTC (Universal Time Coordinates) scale with an accuracy within the microsecond.

The Time Stamp generated by a synchronized TSU at Stratum 1 level, offers an accuracy of 10 microseconds in relation to UTC time.