For word cloud widgets on dashboards, select date range just like date picker shown in the image below:
As of now, text(word cloud) widget allows one to select single date and analyze the pattern. There is no OOTB functionality where you can select range of dates and analyze the pattern.
This requirement can be added to Idea Portal or vote for one (if it is already submitted) by customers so that our Dev teams will review and consider for future releases based upon the feasibility and priority.
Please find the details of Idea Management for customer enhancement requests in the URL below: