What is SAME BAT-TIME, SAME BAT-CHANNEL?

at the end of the 1960s live-action (adam-west) batman tv show, an announcer would tease the forthcoming episode (that resolved any cliffhangars) with the comment: TUNE IN NEXT WEEK. SAME BAT-TIME, SAME BAT-CHANNEL. nowadays it is used to affectionately tell someone that you will see them soon, particularly at a regular-time/place.