I'd start with a site such as this courtesy of Mr. Google. Don't know if it goes back as far as '42 or if vehicle ID numbers back then would reveal that type of info. But since I'm not a GM guy so maybe a GM guru will have a better answer for you. http://www.buickgod.com/header/3238.html
Look on the LOF blip in each window. They're dated, & your car would have been assembled on that or the following month.
Conceived or delivered......?? Putting all seriousness aside, tomorrow I will look up your engine number to get an idea of where it falls in the range for '42 models. That will not be definitive but may help in narrowing the time frame. As you likely know, '42 models were a shortened run for civilian production. I think my reference book(s) may help with that. Ray
1-4257442 was the first serial number for Buicks built at the Flint plant in 1942. 1-4280452 is your number. 1-4364444 was the last. But I don't know what month they stopped production. I think it was early in 42.
There isn't any Buick info on the GM heritage site at all so that is out. I found a tiny bit of info from 2010 but nothing on the month. Going by these two threads 1942 Buick Vehicle Identification - Buick - Pre War - Antique Automobile Club of America - Discussion Forums (aaca.org) 41 Buick data plate decode - Buick - Pre War - Antique Automobile Club of America - Discussion Forums (aaca.org) again long outdated as they are both from 2010 it appears that Buicks like GMC trucks had sequential serial numbers. The best you might hope for is that somewhere in the Buick club archives there is a breakdown as to what serial numbers were month to month.
Ask your question over on the aaca.org website under the Buick section. Someone may be able to give you more info. I spend a lot of time there myself exchanging info on the ‘50s era Buicks.
According to most Buick websites, production ended on 6 February, 1942 for a total production of between 92,000 and 94,000 civilian models . Using the serial numbers provided by Squirrel, it comes out to 107,002. Some of those cars may have been military models, or numbers assigned and never completed. Using those numbers and your serial, I think it is safe to say yours was built in mid January 1942.