X = redate(X,oldDate,newDate)
X [ tseries ] - Input tseries object.
OldDate [ numeric ] - Base date that will be converted to a new date.
NewDate [ numeric ] - A new date to which the base date oldDate will be changed; NewDate need not be the same frequency as OldDate.
X [ tseries ] - Output tseries object with identical data as the input tseries object, but with its time dimension changed.