The real station's second pulse lasts five milliseconds; this one stretches it to thirty so the tick is audible. The time you hear cannot be guaranteed. The real station broadcasts atomic time from Fort Collins, Colorado. This one broadcasts whatever your browser believes.
What the real station does
WWV is the United States time-and-frequency station run by NIST, broadcasting from near Fort Collins, Colorado since the 1960s on 2.5, 5, 10, 15 and 20 MHz (its sister station WWVH is in Hawaii). The format this page keeps is the real one, in outline: a 1000 hertz pulse on every second, an 800 millisecond mark on the minute, the 440 hertz tone during minute two of each hour, a callsign sent in Morse, and voice announcements of the time. Shortwave listeners and calibration labs have relied on it for decades; it is one of the most listened-to radio stations that almost nobody has heard.
What this page changes
Everything is generated in your browser from your own clock. There is no server, no network call after the page loads, and no record of who tuned in. The Morse, the tones and the voice are all produced locally, the way a receiver would produce them from the air. The one thing the page cannot do is be accurate, because accuracy is a promise about the outside world and the page has no access to it. It says so instead.
About the real thing
Sources: NIST's pages on WWV and its broadcast format, and Wikipedia.