HBO Current Circumstances

Local time is read directly from the time setting on your computer. It should always be the same as your local computer clock, as long as the time zone setting on your computer is correct.

Coordinated Universal Time is essentially what is normally referred to as "Greenwich" time, namely, standard time on the prime meridian of the Earth that runs through Greenwich, England.

Greenwich Sidereal Time is computed from the time and the date setting on your computer. If your time is set correctly, but the date is off, then this clock will be wrong even if the previous two clocks are correct.

GST is local sidereal time for Greenwich, England.

Local Sidereal Time describes the meridian of Right Ascension (RA) which is currently transiting the meridian of the sky. At a given LST objects of that same RA are at their highest elevation of the observing evening. LSTs of several hours before or after an objects RA may sink the object too low to make it observable!