Look at the documentation here: https://docs.mendix.com/refguide/xpath-keywords-and-system-variables
You have the
[%BeginOfCurrentMonth%] or the UTC variant. And you can use things like '[%%BeginOfCurrentMonth%] - 3 * [%MonthLength%]' to retrieve other moths. You could also create a variable and use the addmonths function to change dates.
If my assumption is right, you want to have group by your entire dataset by month and pass that dataset to show in graphs.
Without understanding your domain model, it is bit difficult to answer this question.
- Try the suggestion proposed by Ronald
- Or read about OQL in Mendix. With OQL you can write SQL like queries. OQL can be used in report grids. But you can also choose to write a java action, which will execute the OQL and return the dataset so you can process it later the way you need with NPE
If both options does not answer your question, probably rephrase the question with more details
If you want to retrieve the dataset of a single month in a microflow I would do it like this
BUT; I wonder why you want to have multiple lists of data in a microflow. Thus; what is your goal, why do you need them and what do you want to do with them.
Because my gut feeling says that you want to display them in a page as items per month or in a graph. in both cases you don’t need this microflow. ;-)