FormatDuration

Returns the human readable format of the given number of seconds.

• Use TimeSpan.FromSeconds() to convert the number of seconds to a TimeSpan object.
• Use TimeSpan.ToString() with an appropriate format specifier to return a human readable string of the value.

public static partial class _30s 
{
  public static string FormatDuration(double seconds) 
  {
    return TimeSpan.FromSeconds(seconds).ToString(@"d\.hh\:mm\:ss\.fff");
  }
}

_30s.FormatDuration(34325055.574); // 397.06:44:15.574