Expiration date format in PayPlan admin

Hello, In PayPlan admin panel, expiration dates for active subscription are in format "two days ago" "in about one month". I would like to replace those dates with "23.09.2017, 20:36" or "12.12.2017, 23:45"

Could you please tell me how I could modify that?

THanks in advance for your help.

Regards,

Chris