You need to consider which kind of analysis you for which view want - and what this means to the kind of data-model and UI navigation.
For me it looked as if you have just one date-field and you want to display results between one field-value and another field-value. The simplest way to get such view is just to select all (date) values and the expression would be a simple: sum(Sales). In many scenarios this is quite simple and needs just a few clicks - at first on relating year/quarter/month which reduced the amount of possible dates and (usually) adjust the list-box orders. Also possible and not much difficult would be just to use a search on the field with something:
>=date-value1<=date-value2
Beside this a lot of the often queried YTD, MTD, ... the ones from the previous years and many more selections could be simplified with appropriate flags within the master-calendar and/or with an as-of-table.
This means the use of multiple date-fields is not mandatory necessary. Nevertheless is such usability quite common and often implemented per extra variables or like above hinted with date-fields from island-tables. And only with this it would be possible to query independent selections and/or to implement a >= <= logic between them. IMO you should have very good reasons to go in this direction because the above shown selection-approach is more natively and also easier within the development as well as within the user-experience.
