What key am I playing in?

Hello all!  My music theory...um...leaves what to be desired, so please forgive the ignorance I am putting on display here!  So, I have two dulcimers, tuned to GDGG and AEAA (baritone).  I understand that changing the tunings to GCGG and ADAA would change the key I'm playing in... but I don't know to which keys!  Can someone tell me?  Is it just C and D?