The way I achieve this is by having a relative time column in the calendar. A simplified version is something like this diagram below.

You then use the Relative Month column in your dashboard filter bar, and set it to 'Current Month'. The relative month column is pretty easy to calculate based on today. Or you may want to create it as part of a data warehouse refresh job.
One issue with this method is that the relative month columns have to stay static. For example, you couldn't have the relative month column say something like 'Current Month (May-24)'. Such a value would change from month to month so it would be impossible to default to it. (If only dashboards could filter on use/display values like reports can. I have raised this as a change request.)
In order to show users what the Current month is you can either:
- Add a simple table to the dashboard canvas with the Month column, filter this table on relative month.
- Add a cascade filter of month to the filter bar, then users can use the cascade list to see what the current month is.
I also have a blog post ready to go about how to do time trends using this technique which I must get round to finishing.
Whilst I use this technique in the filter bar, it would also work in your scenario of on canvas filters. I am sure you have a reason for using those rather than the filter bar!
(As an aside, you can add prompts to a dashboard by having them in the data module. When the dashboard opens you get an autogenerated prompt for the user to answer. But this is a very poor user interface. And the only way a user can reprompt is to close/open the dashboard. So whilst you can, I have never used it due to this poor UI.)
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Marc Reed
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