Do you mean the total experience of the Party, or a single actor?
To see A single actor's exp use this:
a = $game_actors[actor_id].exp
It should return the current EXP of the actor[actor_id]
Or if you want total EXP of the Party, try:
a = $game_actors.actor[actor_id].exp + $game_actors.actor[actor_id].exp + $game_actors.actor[actor_id].exp + $game_actors.actor[actor_id].exp
This should return the combined values of the EXP of every actor[actor_id] you place in the code. Make sure each ID is different for accurate results...
I'm not sure about play_time though...
If this doesn't work, or you think there may be a better way (and there probably is), go to Tutorials and look in RGSS Tutorials. Go to the link RPG Advocate. It should take you to Phylimortis. There you must look at the default class definitions and see what they tell you.
Hope this helps!
~Broken