iland south of blackbird

i want to get to hte iland south of the blackbird but can you get there

That's the Sun Keep - and you can't get to it in 12000 BC.

You should be able to fly the Epoch to it in 2300AD. It's the same place you see now.

Only after Zeal falls, though. The Sun Keep is available in all eras but 12000 BC, I believe.

Well, you can only fly after Zeal falls anyway.

There are two Sun places. One is where you get the sun stone, and the other is where you charge it up. The former is only available in 2300AD, and I thought it was called the Sun Keep but maybe I am mistaken.

The Sun Keep is that cave that exists in all time periods. The place where the Sun Stone is kept is called the Sun Palace, and it only appears in 12,000 B.C. and A.D. 2300--and is only accessible in the latter period.

BTW, I notice you can't use the Blackbird, and you don't get to it until after Crono dies (in which case you've been captured by that jerk, Dalton).

Off topic, I believe if Crono wasn't dead, Dalton wouldn't have touched a hair on the team's head without getting vaporised on the spot. I still think he deserved a better ending - by which I mean I get to see him scream his unending agony in the eternal hell that is his last moments...