##### UTC

The abbreviation UTC has no formal English or French equivalent but in English speaking countries it is known as Coordinated Universal Time.

UTC is an amalgamation of atomic and rotational time. Put simply, UTC is is an atomic time that 'ticks' at the same rate as the atomic time TA1 but is adjusted at agreed intervals by 1 second (known as leap seconds) to accord with the rotational time UT1 (the old GMT but with subtle adjustments). The Forensic Analyst should be aware UTC is not GMT(UT1), it is close (always within 0.9 second), but it is not the same.

UTC is the time system used for many Internet and World Wide Web standards. In particular, the Network Time Protocol, which is designed to synchronize the clocks of many computers over the Internet. Whenever systems report that a time is GMT or a differential based on GMT (e.g. GMT +6hrs) they are usually wrong and normally refer to UTC. A good example of this is SMTP servers that add 'Received' lines to email messages, the server will normally be using NTP or SNTP timing which is based on UTC, the 'Received' line though will normally report an offset to GMT. We can put this error down to network administrators who fail to recognise the subtle difference between GMT, UT1 and UTC.

##### UTC Resources

- Fisher, R. "Astronomical Times", available to view: http://www.cv.nrao.edu/~rfisher/Ephemerides/times.html#UTC
- Audoin, C., Guinot, B. [2001] "The Measurement of Time", Cambridge University Press, ISBN: 978-0521003971