Hi Chuck,
Not sure how to automate this. However, what would you be looking to do with this data?
The First Active property may not be the best property to look at if you’re trying to figure out time it takes to purchase from visiting your site. The First Active date can be all over the place depending on what info Klaviyo can get from the integration:
If someone first engaged with your organization before you created your Klaviyo account, but Klaviyo was able to sync historical activity through an integration (with your previous ESP, for example), we will set the First Active date to align with the contact's earliest recorded activity. This means it's possible for someone's First Active date to be before their Profile Created date.
I spot checked a few profiles in my account and I don’t think I’d use it. Depending on your goals, maybe the date of a certain action may be more appropriate (ie. Subscribed to List)?
If you’re looking for the days it takes to make a purchase for your overall site, the data in Google Analytics could help there.