:: If you are above 35 degrees longitude you will get NONE for many months of the year. ::
Changes in longitude
Changes in...uhhhh...???
Crap. That’s what I get for phonephagging.
What I assume you intend is to say that if you are NORTH of 55-LATITUDE, you will not get enough [direct] sunlight to metabolize your natural levels of Vit-D.
Latitudes are measured from zero at the equator and encircle the globe, extending to 90-North and 90-South.
At latitudes above 55 North (90-35), the sun does not traverse the sky higher than 35-degrees.
55-North is somewhere in Canada (Hudson Bay, maybe?)