[Freeswitch-users] fs_cli | show calls | answer timestamp

Hello All! I use fs_cli api for interraction with FS from my application. Now I wish get current active calls (api show calls) and calculate current duration. "show calls" output many fields, but timestamp represent call originate time and no one field with timestamp represent b_leg answer time (SIP 200 OK message) So, any idea (easy implementation) to obtain SIP 200 OK timestamp or current call duration since 200 OK received? Dmitry