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Chaos Game


Sidereal and Solar Time Clocks

The Java applet displays clocks for Universal Time, Greenwich Sidereal Time,
Zone Time, Local Sidereal Time,
Local Solar Time and Greenwich Solar Time.

To change the settings uncheck the Run box before:

Select a location from the menu list, or enter the coordinates (decimal degrees)
for latitude (northern positive, southern negative), and longitude (eastern positive, western negative),

and hit the button "Apply input"


The applet will adjust the timezone. As there are no definite rules for daylight saving time, check the time offset to get the correct local times.

You may use the keys "h", "d", "m" to increase the hour, date, or month,
Shift key and "h", "d", "m" to decrease the hour, date, or month !

The Apparent Solar Time

is measured by a sundial and is based on the actual daily motion of the real Sun.
Apparent solar noon is the time when the Sun crosses the meridian of the observer. The apparent solar day is the interval between two successive meridian passages.

Zone Time

There are 25 integer World Time Zones from -12 through 0 (GMT) to +12. Each one is 15 of Longitude as measured East and West from the Prime Meridian at Greenwich.
To convert the apparent solar time the corrections are:

  • Correct for longitude. For every degree of longitude that the sundial is west of the time meridian add four minutes to local solar time (the sundial reading) to give meridian time. For every degree east, subtract four minutes.
  • To get mean time from meridian time add the Equation of Time.
  • When summer time is in use, add one hour.

The Sidereal Time

is measured by the rotation of the Earth with respect to the fixed stars.
Because the earth moves in its orbit about the sun, the sidereal day is about 4 min shorter than the solar day.
Applet by Walter Fendt

The Local Sidereal Time

of an observer is equal to the hour angle of the vernal equinox or the right ascension of the meridian, or
Hour Angle + Right Ascension = Sidereal Time
Applet by Walter Fendt


You may edit the applet parameters
using a html editor or Window's editor:
<applet code="SidSunClock090.class" archive="JavaClasses.jar"
 align="bottom" height="600" width="600">
<param name="password" value="14365">
<param name="email" value="Thanks for registration">
<param name="location" value="Berlin">
<param name="latitude" value="52.51">
<param name="longitude" value="13.41">
<param name="timezone" value="1">
<param name="daylightsaving" value="1">
<param name="sun" value="1">

Web Links

World Time Zone Map with current time

Countries/Territories operating Daylight Saving Time, 2006

Compute Local Apparent Sidereal Time (USNO)

Location Database (Heavens-Above)

A Matter of Time


Sidereal Time only

Local Hour Angle and Local Sidereal Time

please visit my GeoAstro Applet Collection

Updated: 2023, Oct 06