This pattern describes how to compute month-related calculations such as year-to-date, same period last year, and percentage growth using a month granularity. This pattern does not rely on DAX built-in time intelligence functions.
You can use the Month-related calculations pattern if the analysis over sales is executed at the month level (or above) only. In other words, the formulas stop working if you drill down to the date level. Because the pattern does not use real dates to link to sales, you can also implement fiscal calendars with 13 months and any non-standard time-related calculation – provided that the maximum level of detail of the reports is the month and not weeks or days.
In case your requirements cannot be fulfilled by month-related calculations at the month granularity, then you should use another pattern. Check the Time-related calculations introduction to figure out what is the right pattern for your scenario.