Question

I am looking for a Regular expression to match only if a date is in the first 28 days of the month. This is for my validator control in ASP.NET

Answer 1

Don’t do this with Regex. Dates are formatted differently in different countries. Use the DateTime.TryParse routine instead:

DateTime parsedDate;  if ( DateTime.TryParse( dateString, out parsedDate) && parsedDate.Day <= 28 ) {  // logic goes here. } 

Regex is nearly the golden hammer of input validation, but in this instance, it’s the wrong choice.