Last N months

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Dynamic Rolling Period Slicer

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Key Features

Your line or bar chart shows the full history, but you'd rather let readers zoom into a recent window they set themselves. The obvious tools let you down: a fixed date filter goes stale the moment the calendar ticks over, and Power BI's built-in relative date filter stops behaving once there's a year slicer on the page. And there's a subtle trap — when someone picks 2024 and a 13-month window, they should see December 2023 through December 2024, not just 2024. Getting the slider, the chart axis, and the year slicer to agree on that takes a lot of trial and error to build by hand.

This skill builds the whole thing in one go and drops a slider on the page that readers can drag themselves — run it with /last-n-months.

How it works

Type /last-n-months, point it at your chart, and it asks two quick questions before building everything:

Looks at your model — finds your calendar table, its date columns, your fact tables, and anything compatible that's already on the page
Shows you what it found — the calendar shape, the measures it picked up, and the tables it can anchor to
Asks two things — the slider range (1–15 months by default, starting at 12) and which table the window should count back from
Builds it — the supporting tables and measures, a slider on the page framed by "Last" and "months" labels, and the chart rewired to follow the window
Saves it to your project — open in Power BI Desktop to see it working

What you get

A slider on the page — framed by "Last" and "months" labels, with the starting window you chose
A chart that follows the slider — drag it and the chart redraws to that many recent months; months outside the window simply drop off (no visual-level filter behind it)
A self-updating title — names the active window, e.g. "Last 12 Months (Jan 2014 – Dec 2014)"
A reliable window end date — one consistent point the window counts back from, matched to your calendar
Correct bars every time — each month shows its true value even when a year slicer is also in play
The plumbing behind it — the small helper tables and wrapper measures that make the window work, added for you

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