There is no “date” data type in COBOL, but there is in DB2, where the data would be saved, unless they are on an older VSE OS and data is still saved in VSAM files. Many still use 12/31/39 as a default max date even though OS/400 systems can handle up to year 9999 now (we still use 12/31/39 in testing where I work). It could be someone arbitrarily started using 1875, and others copied that.

Mainframe does what it does very well, and that makes it okay.

Just in case you didn’t know, the code is old, but the hardware still gets updates. And when it comes to batch transactions and network speed, mainframes still do the job reliably well. Plus, they are not easy to hack, because few understand them, not to mention the decades of security updates.

I’m agnostic about other gods but my religion is not believing in the Abrahamic god as described in the bible.

It’s impossible to represent that on paper. It could be misrepresented as a specific number of spaces. Depending on the position on the paper, it may also be hard to tell if the carriage return comes with the line feed. Unless you want the document to be in ASCII or EBCDIC hex, it’s like writing an ambiguous math problem where the answer is different depending on how you were taught about the order of operations. Don’t do this to your kid, Abcde.