I recently saw a meme that said the person was not setting their clocks back because they do not want an extra hour of 2020.  Welcome to the Fall season which officially started on September 22nd.

As we move into colder weather it is natural to not get as much sunlight on our skin as we cover up more of it.  This is an annual change that we experience which happens sooner and with greater severity with increasing distance from the equator.

The three ways to increase your intake of Vitamin D are by sunlight, eating foods rich in it, and through supplements.  Why is Vitamin D so important? Although named Vitamin D, it is actually a hormone.  

Vitamin D is required to absorb calcium from the gut into the bloodstream, and has several other well-known mechanisms in the body.  There is also some evidence that daily supplementation with 1500 IU of vitamin D3 plus 20mg of Fluoxetine (Prozac) was superior to Fluoxetine alone in Major Depressive Disorder*.  

So if someone is not eating enough foods rich in Vitamin D, not getting it from the sun, then this is where supplements come in.  

*https://www.medscape.com/viewarticle/896449