正则表达式匹配当前年份日期

Question

I just started to learn regex. I created a regex for my project username where I want:

• 2 digits of day

• 2 digits of month

• last 2 digits of current year

• finally last 2 digits of the year after 4 years

ie I need to match output something like that:

23071923

where:

• 23 is the current day(dd)

• 07 is the month (mm)

• 19 is current year(YY)

• 23 is the year after 4 years(yy)

But I am confused how will it match the current year and only take last 2 digits of the year. and how i can match the end of regex is correct and is 4 added in the year or not?

Answer 1

You could use the trick with replacing the input string with modified string, which does math:

var x = "23071923";
var x2 = Regex.Replace(x, @"^(\d{2})(\d{2})(\d{2})(\d{2})$", m =>
         m.Groups[1].Value + m.Groups[2].Value + m.Groups[3].Value +
         (int.Parse(m.Groups[3].Value) + 4));
bool is_match = x == x2;