Probably not the right answer..

We are not twins:

You're two of triplets. So you're not twins.

Born a day after me:

Born just before/after midnight. So two separate days.

Where am I:

This is where I can't find anything relevant.

Probably not the right answer..

We are not twins:

You're two of triplets. So you're not twins.

Where am I:

On a boat, crossing the International Date Line

Born a day after me:

Born a few seconds apart, crossing over the International Date line, making you born roughly 24 hours apart.