I admit that I use a somewhat long-winded bash prompt:
--(username)-(Wed April 01|12:00:00)--(~ $
Recently, I got the bright idea to change
You just seem to be missing the start and end brackets around your escapes (before the first '\e' and after the last 'm'):
PS1='--(\[\e[$((32-${?}))m\u\e[0m)-(\e[$((32-${?}))m\d\e[0m|\e[$((32-${?}))m\T\e[0m)--(\e[$((32-${?}))m\w\e[0m\] \$ '
As mentioned, the PS1 var does not need to be exported: only your shell needs to see it.