There was a time when data structures were made to fit purpose, not compilers. Having a look at the subject, shows clearly the constrains for valid dates:
Social Security was introduced in 1935.
To be eligible for benefits one had to
pay in at least 40 quarters, that's 10 years
be at least 65 years old
This means the first regular beneficiaries of social security payments were 65 in 1945, aka of the 1880 cohort. Virtually noone participating in this system can be born before 1880. Anyone older will not most likely not be a beneficiary, and anyone younger (aka still paying in) will be, well, younger.
So add another 5 years for wiggle room and we end at a nice round 1875 as earliest year for any birthday to be recorded.
A perfect rational base for a date entry, isn't it?
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The "COBOL doesn't work like that" comments are missing the forest for the trees: This is a very old system with bespoke coding to match legislation, not legislation to match compiler default behaviour.
Fundamentally, unless a government employee that has worked directly on this codebase speaks up, we're all just guessing.
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There was a time when data structures were made to fit purpose, not compilers. Having a look at the subject, shows clearly the constrains for valid dates:
This means the first regular beneficiaries of social security payments were 65 in 1945, aka of the 1880 cohort. Virtually noone participating in this system can be born before 1880. Anyone older will not most likely not be a beneficiary, and anyone younger (aka still paying in) will be, well, younger.So add another 5 years for wiggle room and we end at a nice round 1875 as earliest year for any birthday to be recorded.
A perfect rational base for a date entry, isn't it?
----
The "COBOL doesn't work like that" comments are missing the forest for the trees: This is a very old system with bespoke coding to match legislation, not legislation to match compiler default behaviour.
Fundamentally, unless a government employee that has worked directly on this codebase speaks up, we're all just guessing.