This is an animation of the way the sun illuminates various time zones in the northern hemisphere. The time zones are
labeled +/-12 depending on their longitudinal angular distance from Greenwich, England (GMT). For regions to the west of GMT, the
zones are negative up to -11 hours, for example NYC is time zone GMT-4. To the east of GMT the zones are positive and labed 0 to 12, for example the
time zone of Bagdad, Iraq is GMT+3. The Sun is shown at the bottom of the window and it illuminates the botton of the ellipse while the
ellipse rotates. The point of observation is the small circle on the ellipse.
The small circle can be rotated using the longitude slider and it can be moved nearer the center (closer to the North Pole) using the
latitude slider. The hour slider rotates the entire ellipse once for a range of 360 degrees.