PowerPivot Time Calculations
A recommended practice for implementing time calculations in PowerPivot is to have a Data table with a datetime column. Kasper de Jonge explains in more details in this blog. This approach will probably save effort when importing data from normalized schemas and won't require specifying additional arguments to the PowerPivot time functions. However, it will undoubtedly present an issue when importing data from a star schema. A dimensional modeling best practice is to have an integer key for a Data dimension table in the format YYYYMMDD and integer foreign keys in the fact tables. Luckily, you don't have to normalize data back to datetime when building a PowerPivot model on top of star schemas after the issue with the All filter Kasper reported a while back got fixed in PowerPivot RTM.