Calculating the latitude of the sub-solar point

The key to understanding seasons and length of daylight is to know the date and location of the sub-solar point. Once you get these, you can figure out the seasons and hours of daylight for any location on Earth.

Four dates are straightforward; you’ll figure these four out by memorizing the following table:

Calculate every other day of the year by finding the two dates that come before and after it on the table. For example, October 1st falls between September 22 and December 22nd like this:

So we estimate that the latitude of the sub-solar point on October 1st is between the equator and 23º South.

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Practice Questions

What is the date when the sub-solar point is at 23.5 deg South?