There used to be such a page, I don't know if it still exists or not, but in all honesty using the avast tray icon (right click), About Avast should do it. Release date and time may well not match your date and time group.
Mine currently reports 210312-0, which is todays VPS, you can go into the AvastUI > Menu > Settings > Update and that will show you what you have and if it is up to date or not.
If you have Auto Update for virus definitions you should have the latest version, there are also the Streaming Updates and these keep coming (every few minutes if always on-line) until you receive another VPS update. This would have all of the previous streaming updates, so these would be initialised a would start again from that VPS update.