Honestly though, there is no way to predict the behavior of these functions with the documentation provided. I suppose that I should just be happy that these functions actually do something relatively difficult at times versus being sugar syntax for MAX, MIN or CALCULATE. Poorly documented, unintuitive FILTER functions with, frankly, some relatively bizarre behavior at times. Sure, there is some tricky date manipulation stuff going on, especially with quarters but at the end of the day, these functions are all just glorified FILTER functions. There is perhaps a parallel universe where I might have some grudging respect for these functions. This post covers DATEADD, SAMEPERIODLASTYEAR, DATESINPERIOD and PARALLELPERIOD. OK, I believe this one should put the final nail in the coffin of Time 'Intelligence' functions in DAX.
