Regular expression where part of string must be number between 0-100

Question

I need to validate serial numbers. For this we use regular expressions in C#, and a certain product, part of the serial number is the \"seconds since midnight\". There are

Answer 1

With the standard 'this-is-not-a-particularly-regexy-problem' caveat,

[0-7]\d{4}|8[0-5]\d{3}|86[0-3]\d{2}|86400