/// <summary>
/// Stretches the current time span by multiplying its length by the specified multiplier.
/// </summary>
/// <param name="multiplier">Multiplier to stretch the time span by.</param>
/// <returns>Time span that is the current time span stretched by the <paramref name="multiplier"/>.</returns>
public ITimeSpan Multiply(double multiplier)
{
ThrowIfArgument.IsNegative(nameof(multiplier), multiplier, "Multiplier is negative.");
return(new MathTimeSpan(TimeSpan1.Multiply(multiplier),
TimeSpan2.Multiply(multiplier),
Operation,
Mode));
}