.NET quick samples: Up-times, ages, rounding to n places

using System.Diagnostics;

public TimeSpan GetUptime() {
    var systemUpTime = new PerformanceCounter("System", "System Up Time");
    systemUpTime.NextValue(); // Required to work!
    return TimeSpan.FromSeconds(systemUpTime.NextValue())));
}

public int GetAge(DateTime birthday) { 
  return DateTime.Now.Year - birthday.Year - 
      (((DateTime.Now.Month < birthday.Month) || 
      (DateTime.Now.Month == birthday.Month && 
      DateTime.Now.Day < birthday.Day)) ? 1 : 0);
}

public decimal ArithmeticRound(decimal d, int decimals) {
    var power = (decimal)Math.Pow(10, decimals);
    return (decimal.Floor((Math.Abs(d) * power) + 0.4m) / power) * Math.Sign(d);
}