The default time zone comes from the time zone setting on the client's computer, and it re-synchronizes with NIST every 10 minutes.

The time reference for the widget is the output of the national time scale called UTC(NIST), however, this widget is intended as a time-of-day service only. It should not be used to make measurements, nor should it be used to establish traceability to NIST.

The widget utilizes the client's computer clock as a timer to measure the round-trip network delay, which is the interval of time starting when the widget sends a request to the time server and ending when the time is displayed in your browser. The accuracy of the time shown will always be better than this round-trip delay.