Convert a two digit year to a four digit year

Question

This is a question of best practices. I have a utility that takes in a two digit year as a string and I need to convert it to a four digit year as a string. right now I do <

Answer 1

If you calculate for a person he will probably not be more than 100 years...

Eg: 751212

var nr = "751212";
var century = DateTime.Now.AddYears(-100).Year.ToString().Substring(0, 2);

var days = (DateTime.Now - DateTime.Parse(century + nr)).Days;
decimal years = days / 365.25m;
if(years>=99)
 century = DateTime.Now.Year.ToString().Substring(0, 2);

var fullnr = century+nr;