A date table is essential to data work, whether you’re working in SQL, Tabular Modeling for Power Pivot, Power BI or SSAS.
Because if you work with any kind of data, and particularly accounting data, you’ll always have to ask for the appropriate time period.
You can find lots of good examples of how to build a data table, both in SQL and in Power BI, if you operate on a calendar year or your fiscal months are calendar months.
Google is your friend here, so if the links above don’t help, you can find others.
But, if you’re a retailer or another business that operates on some variety of a 4-5-4 calendar (with a 53rd week showing up every couple of years), that’s not as easy to find.