Chassis code and build dates, decoding VIN and Chassis codes for dates of build- my number appears later than known delivery Options

[DRPHIL914]

i was recently researching the chassis number decoding and there is another older thread about this. Based on that information , my chassis number of 472-9075
states that my chassis was built in the 47th week and 2nd day do the 1975 model year.

BUT weren’t some 75’s built in late 1974? so what is the first month of the model year build is it January 1975 or is it October of 1974?

my car birthday according to my COA is Sept 15, 1975. it was special ordered L99k color with full appearance group. it was offered and money deposited in the summer of 1975 and it was delivered and paid , picked up on October 15, 1975.
so how can the chassis build date be 47th week? that would put it in November 14 or so of 1975 if you go tomorrow January 1 for the calendar year.

Phil