Change in Time Bucket from Week to Day

We are planning for a demo in Demantra stand alone syetm (version 7.3.1.4)  with time bucket as day. current time bucket set up is week. At present we have data in Demantra with Time bucket as week.  We want to change the time bucket to day (through data Model)  without affecting the existing data in current demantra instance.

 If we change  the time bucket from  Week to day what would be impact of the existing data in demantra Instance. If so if there is any other method to change the Time bucket without having impact  in existing  data. Suppose after the change in time bucket (Week to day) , if the old data is shown in day's bucket  instead of Week's bukcet is also fine. Please suggest.