using System;

​

Func<string, string> m = (x)=>$"{System.DateTime.Parse(x).AddMinutes(1):HH:mm}";

​

Console.WriteLine(m("00:00") == "00:01");

Console.WriteLine(m("00:02") == "00:03");

Console.WriteLine(m("05:55") == "05:56");

Console.WriteLine(m("09:59") == "10:00");

Console.WriteLine(m("12:49") == "12:50");

Console.WriteLine(m("20:05") == "20:06");

Console.WriteLine(m("23:59") == "00:00");