PREVIOUSMONTH: what is the underlying Calculate+Filter in DAX?

[lockmirbee]

Unfortunately i'm working for a company that doesn't report on a week or month basis, but on a period basis. Every quarter has 3 periods: of 4, 4 and a 5 week period. Therefore, i can't use time-intelligence functions like PreviousMonth to jump between Periods.

Luckely my dataset always has the Periodnumber + ISOyear in the dataset, and lower levels like weeks and days are never relevant for me as financial reporter. So i've tried making Fake date-column like so: DATE([Isoyear],[Period],1), so I could start using time-intelligence functions.  Unfortunately this didn't work, not sure why.

I recall that Previousmonth-function wasn't available in the early days of PowerBI, and instead everybody used a Calculate+filter(+ALL?) function. I'm having a hard time finding this syntax, does anyone know what it was? I'd like to try this to solve my problems.

[amitchandak]

@lockmirbee , With help from year period YYYYPP, if you can create a rank column you can work with that

example, new column in date table

Period Rank = RANKX(all(Period),Period[year period],,ASC,Dense)

Measures

This Period = CALCULATE(sum('Table'[Qty]), FILTER(ALL(Period),Period[Period Rank]=max(Period[Period Rank])))
Last Period = CALCULATE(sum('Table'[Qty]), FILTER(ALL(Period),Period[Period Rank]=max(Period[Period Rank])-1))

explained in

Time Intelligence, DATESMTD, DATESQTD, DATESYTD, Week On Week, Week Till Date, Custom Period on Period,
Custom Period till date: https://youtu.be/aU2aKbnHuWs&t=145s

Power BI — Month on Month with or Without Time Intelligence
https://medium.com/@amitchandak.1978/power-bi-mtd-questions-time-intelligence-3-5-64b0b4a4090e
https://www.youtube.com/watch?v=6LUBbvcxtKA