C#

static bool IsDateTimeOk(string input)
{
	try
	{
		int year = int.Parse(input.Substring(0, 2)) + 2000;
		int month = int.Parse(input.Substring(2, 2));
		int day = int.Parse(input.Substring(4, 2));
		int maxDaysInFeb = 28;

		if(year % 4 == 0 && year % 100 != 0 && year % 400 == 0)
			maxDaysInFeb = 29;

		if(month == 1 || month == 3 || month == 5 || month == 7 || month == 8 || month == 10 ||	month == 12)
			if(day >= 1 && day <= 31)
				return true;
			else if(month != 2)
				if(day >= 1 && day <= 30)
					return true;
				else
					if(day >= 1 && day <= maxDaysInFeb)
					return true;

		return false;
	}
	catch
	{
		return false;
	}
}