Hi dude,
Sunlight is very important as it not only increases serotonin but provides you with vitamin D, which you cannot synthesize without it! Vitamin D gives you protection from multiple sclerosis, diabetes, cancer, hypertension, asthma & allergies, heart disease and stroke because it modulates immune responses and, vitally, gene transcription. More than 2000 genes are upregulated by vitamin D and it can affect your mood just as much as being short of serotonin.

It is very important to replace this vitamin with supplememtation if you don't get natural sunlight, but you should always try to get some sunlight every day if its available. I take my breaks outdoors in good weather -even ten minutes twice a day is helpful. And there are weekends! You still get some when it's cloudy.

Remember that as much of your skin as possible needs exposure -not just the face and hands. When it's nice enough, get into those short sleeves and shorts  :  )

Obviously don't go over the top and spend 4 hours on the beach a day -little and often is much better for immunity than lots all at once. Behind glass (eg, in cars or through windows) doesn't count because the part of the spectrum you need to make vitamin D can't pass through glass.

If you have light skin you need less exposure than if you're dark skinned, but many westerners are currently vit-D deficient.

Serotonin is also boosted by some soil bacteria, so it's good to get your bare feet or hands on the earth sometimes too.

Having said all this, if your serotonin levels are fine you don't need to go chasing more, but you do need contact with sunlight for that all-important vitamin D.
Best,
AR

Hi dude,
There is a lot of controversy about sunscreen, some claiming its ingredients can make some people MORE susceptible to cancer than going without (see: Mercola.com)

I never use it, preferring to cover myself with light cloth as sun protection rather than products, after an initial exposure. Lab sleeve-protectors are good, so is a pillowcase or white scarf on the head with a headband such as saudis use, which keeps face and head in the shade and absorbs sweat too. Costs nothing, looks eccentric, keeps insects out of your face, avoids both toxicity from products and  over exposure to UVA.

Re: serotonin production:
You photosynthesize vitamin D from sunlight & nutrient precursors. You don't photosynthesize serotonin. Putting suncream on your hands or the bottoms of your feet will stop you absorbing so much serotonin from soil (so will shoes and gardening gloves) but there are a lot of factors in being outdoors that can boost the production of serotonin, including natural surroundings, relaxing, warmth, light and pleasant smells. None of these will be affected by sunscreen, obviously!

Remember you can also boost transmitters and vitamins with foods that provide their precursors.
Best,
AR