[aqrit]

There are two digits for months. A check is required per-character to prevent bad chars (e.g 0x3A) from being laundered by the multiply. The '19' comes from fact that the first digit may be only 0 or 1, while the 2nd digit maybe any value 0..9 (e.g September '0'9' October '1'0'). The second check catches bad month values between 13..19 which were not caught by looking at individual digits. Realistically, the first check may be overbuilt, it only needs to check is_digit or not, but it still has to ignore the padding bytes at the end, somehow. Now... I believe there would be a problem with the month value of '00'... because it unconditionally subtracts 1 from that field then uses it as a table index.

[carlsborg]

Ok 8 bit unsigned ints and zero padded month, and then they do the zero saturated subtract. I hadn't made it to the second check, doh.