Automating a policy review process using reminders and different boards

Hi everyone. I’d welcome your thoughts on the following challenge:
I have set up a simple policy library in Policies can be filtered by theme (HR, data protection etc) and review frequency is captured in a number column (3 months, 6, 12, 18 and 24).
I would like to automate the review date column, so that when a policy under review or development changes its status to Active, the publication date is set to today and the review date is today plus the corresponding number of months.
But, I can’t figure out how to combine a number column with a date column to generate another date. The key point is that different policies have different review intervals determined by their type, and I want to avoid having to manually set the review date for each.
Thank you for your thoughts.

Happy to report I’ve figured this out. I used an automation so that when Status changes to Live, Publication date is set to Today, Review date is set to Today, and then Only if the Category is x, Push the Publication Date by n months. So, the HR category pushes by 6 months, the data category by 12 months etc. I hadn’t immediately realised that I had to set the Review date to today first, before I could push it. I’m now trying to work out how to ensure only one label is permitted in the category column - this doesn’t seem possible, so I might have to use a different form of category or status.