The direction in which the Sun sets changes from day to day. If you watch sunsets from the same location for a year, then you'll notice that the Sun sets a little further towards the south each day between 21 June and 21 December, and a little further towards the north each day between 21 December and 21 June. Around 21 June, the sunsets is furthest to the north, and around 21 December it is furthest towards the south. Around 21 March and 23 September, the setting Sun is almost due west.
You can read the rest at the link below:
http://www.astro.uu.nl/~strous/AA/en/antwoorden/zonpositie.html#v31
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