How to change passphrase of gpg keyring

On my OpenIndiana I have gpg2 installed.
The keyring is from an older installation, with an old passphrase.

To change the passphrase list your keys with
gpg2 -k

after this you can edit the key with
gpg --edit-key <your key>

on my side, a GTK Dialog opens to request the old and the new passphrase.

seahorse is a GUI app to do the same, available in the OpenIndiana repo