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

Generate a Regular Expression to Match an Arbitrary Numeric Range http://utilitymill.com/utility/Regex_For_Range

yields the following regex expression:

\b0*([0-9]{1,4}|[1-7][0-9]{4}|8[0-5][0-9]{3}|86[0-3][0-9]{2}|86400)\b

Description of output:

First, break into equal length ranges:
  0 - 9
  10 - 99
  100 - 999
  1000 - 9999
  10000 - 86400

Second, break into ranges that yield simple regexes:
  0 - 9
  10 - 99
  100 - 999
  1000 - 9999
  10000 - 79999
  80000 - 85999
  86000 - 86399
  86400 - 86400

Turn each range into a regex:
  [0-9]
  [1-9][0-9]
  [1-9][0-9]{2}
  [1-9][0-9]{3}
  [1-7][0-9]{4}
  8[0-5][0-9]{3}
  86[0-3][0-9]{2}
  86400

Collapse adjacent powers of 10:
  [0-9]{1,4}
  [1-7][0-9]{4}
  8[0-5][0-9]{3}
  86[0-3][0-9]{2}
  86400

Combining the regexes above yields:
  0*([0-9]{1,4}|[1-7][0-9]{4}|8[0-5][0-9]{3}|86[0-3][0-9]{2}|86400)

Tested here: http://osteele.com/tools/rework/