I'm working on an eCommerce website where we list products from multiple vendors, and the products a user can buy varies throughout the day based on a pre-set schedule.
For example, something might be available only after 2PM on Wednesdays, or only between 11 AM and 3PM on weekdays.
We don't want the search engine rankings to be strongly affected by the time of day that the crawler visits the site.
We also cannot show the user products that are unavailable - they can only be shown things they can buy based on the time they visited.
So is detecting the crawler and giving different results the best way to go? Or are there other options I'm not aware of? Are there SEO penalties to showing different content to the crawler, and if so are there any ways to mitigate that?