The above app is called D-minder. It’s useful for Northern bros.
Depending on your altitude and longitude you might not be able to get vit D more than a few months a year.

Of course the sun’s rays are more than just vitamin D inducing, but it’s a great way to measure. More vit D from the sun = more benefits, simple as.

https://vitamindwiki.com/No+–+10+minutes+per+day+of+sun-UVB+is+NOT+enough

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