Events-In-Progress for Time Periods in DAX

Calculating the Events-In-Progress is a very common requirement and many of my fellow bloggers like Chris Webb, Alberto Ferrari and Jason Thomas already blogged about it and came up with some really nice solutions. Alberto also wrote a white-paper summing up all their findings which is a must-read for every DAX and Tabular/PowerPivot developer. However, I recently had a slightly different requirement where I needed to calculate the Events-In-Progress for Time Periods - e.g. the Open Orders in a given month - and not only for a single day. The calculations shown in the white-paper only work for a single day so I had to come up with my own calculation to deal with this particular problem.