Timing of Presidential Elections in California

SB 113--the CA February primary bill--apparently has left its last committee of the California legislature as of Monday and will likely soon be on our Governor's desk. I was looking at the text of this bill and it says the date of the primary will be, if the bill is not vetoed, on "the first Tuesday in February in any year evenly divisible by the number four."

A fellow student asked me "Why 'divisible by four' and not 'the presidential election year'?" I can't seem to easily figure this one out. 3 U.S.C. §1 says "in every fourth year succeeding every election of a President and Vice President." Which seems to bootstrap the year of presidential (and vice-presidential) to the presidential election before 1845 when Congress passed that law. So, if Congress chose to change the date of the pres./vice-pres. election to a year not evenly divisible by four, the CA Election Code would have to be revised accordingly.

I guess I can see that having presidential elections in years divisible by four, which are typically leap years, would give one extra campaign day, but I still don't understand the CA Election Code's "divisible by four" language. I suppose it could possibly be just a statutory construction matter (that is, the other dates listed in CA Elec. Code §1000 are stated in terms of divisibility).

I guess I'm stumped.