permalinks after update

I did an update and all went well, but did not remember how my permalinks had been set up before. I think it was a custom string.

Now the permalinks are on the default, date and title. All the old posts come up in that form.

Does this matter — does it create any problems with Google/the archives? Or can I just go ahead and set the permalinks as I like.

And/or — is there a way to tell what the old permalinks url structure was, esp. if it matters. I backed up DB and files. Thanks.