Site Map


                      applet, clock
                    applet, clock
Chaos Game
                      applet, clock
                    applet, clock


Solar and Lunar Time

Enter latitude in decimal degrees:
northern latitudes positive, southern negative,
and hit RETURN key.
Enter longitude in decimal degrees:
eastern longitudes positive, western negative,
and hit RETURN key.

Select your time zone:
east of Greenwich positive, west of Greenwich negative.
keys  shift
You may use the keys "h", "d", "m", "n" to increase the hour, date, month, or minute,
or shift key and "h", "d", "m" , "n" to decrease the hour, date, month, or minute !
Click the applet first !

azimuth angle

The Local Solar Time is 12:00 when the Sun crosses the north-south meridian reaching its highest point in the sky (measured by a sundial). It differs from local standard time according to longitude, time zone, and equation of time.

The Local Hour Angle
of a heavenly body is the angular distance from the observer's meridian to the local meridian of the body, measured on the celestial equator westward from the local meridian through 360, normally expressed in time-units (h, m, s).

Both clocks of my applet are using the local hour angle (of the Sun or the Moon):
The clock time is 12:00 at upper transit, and 0:00 at lower transit (minimum altitude).
The gray sectors are given by the times of rise and set, also
using the local hour angle.

A lunar day (also called tidal day) is the time required for the earth to rotate once with respect to the moon, or the interval between two successive upper transits of the Moon over the meridian of a place. The mean lunar day is approximately 24 hours and  50.4 minutes (24.84 solar hours) in length, or 1.035 times as great as the mean solar day.

Conversion of standard time to local solar time:

Example: Berlin, time zone UT+1h, longitude 13.41 E,
on 2007 Mar 24 at 22:28 standard time (CET).
The correction for longitude is 4 minutes per degree of difference between the
local longitude (13.41 E) and the longitude of the standard time meridian (UT+1h is corresponding to 15 E):

longitude correction
equation of time
total correction
standard time local solar time
4*(13.41-15) min =
-6.36 min = -6 min 22 s
-6 min 16 s 
-12 min 38 s
  22:28:00 22:28:00 - 12 min 38 s =

Lunar days in 2007: variation between 24 h 38.5 min (Jan 9/10) and 24 h 66.5 min (Nov 25/26)
2007 avarage: 24 h 50.446 min = 24.8408 h
2007-2037 avarage: 24 h 50.471 min = 24.8412 h

Lunar day

Select "Rise/Set Moon" from the "Details" menu:

Rise Set Moon


So far, the Moonlight diagram is not working correctly for high latitudes > 61.4 = 90 -(23.44+5.14),
where the Moon can be visible/unvisible for  several days. 

Table: select "Lunar Transits" from the "Details" menu.

Full Moon dates

Table: select "Full Moon" from the "Details" menu.

Full Moon

Full Moon on 2007, Apr 2 at 17:16 UT
Local upper Moon transit
on 2007, Apr 3 at 00:15 local time,
lower transit of The Sun.

new Moon

New Moon on 2007, Apr 17 at 11:36 UT
Local upper Moon transit
on 2007, Apr 17 at 11:00 UT,
Local upper Sun transit on 2007, Apr 17 at 11:06 UT.

map declination longitude

2007 Mar 24 at 21:28 UT
Sun: LHA Berlin = 153.8
, declination = 1.5 N
Moon: LHA Berlin= 75.3, declination = 28.5 N

Web Links

Aluna - the world's first tidal powered Moon Clock

Mean lunar and solar periods

Coastal Processes and Tides

Gnomonic: see "Moon Clocks"

Moon dial

Queens' College Dial


A Moondial

Claudius Franciscus Milliet Dechales: Cursus seu mundus mathematicus (1674)
Propositio XXXI - Horologia Lunaria

Analemma of the Moon (Astronomy Picture of the Day)

Les Cadrans Lunaires

Lunar Sundials

Updated: 2023, Oct 07