How old is a cat with no "bred date" shown in cattery?

[Arwen Swordthain]

One of the easiest ways to check would be by looking at the traits and checking the discovered dates on those. If all the traits were discovered before the earliest date you see then I'd guess your assumption is correct. The online cattery was launched in April 2012 so its possible they didn't start adding box drop dates until around that time in one of the previous updates.
Another way to check dates is to look at the baby via its parents page, if you bred the box of course and Menageried or kept the parent. Box birth dates show on the parents page.