Depending on where you are and what/when you work you might not be able to "just go outside" at that specific time.

Cold, dark Canada in the winter :(

But you are right, the sun is the best original source.

It is currently 11°F with 14mph wind here

I promise I'm not trying to be that-guy, but cold or not, that sun exposure should still work and cold is good. it's uncomfortable, but it's not inherently 'bad' per se.

Honestly, that sounds like a beautiful winter day. Would be perfect to go skating or cross-country/downhill skiing in. Playing hockey, I doubt I'd even wear a jacket.

That puts the wind chill at -5°F. Won't be getting any rays bundled up for that.