I'll list the steps!
1. Go to your Profile.
2. Click the "Shop" tab that's located on top of your VMs and that's with others such as "About Me", and "Wifi/Trade Rating.
3. There, you'll see your collectibles in a list, under the description is the date of it!
Coolectibles are then listed in order from "oldest" to "youngest", the earlier/later the collectible, the first/last ordered.