public JsInstance SetDateImpl(JsDictionaryObject target, JsInstance[] parameters)
{
if (parameters.Length == 0)
throw new ArgumentException("There was no date specified");
DateTime valueOf = CreateDateTime(target.ToNumber()).ToLocalTime();
valueOf = valueOf.AddDays(-valueOf.Day);
valueOf = valueOf.AddDays(parameters[0].ToNumber());
target.Value = valueOf;
return target;
}