O2 sensor confusion

I do not have a code reading B1 or B2. I am replacing the O2 sensors because the car is down for a while. I bought the sensors A/C Delco 213-1165 (right upstream) and A/C Delco AFS21 (supposed to be Left Upstream). As crazy as it might sound left and right sides of the engine appear to flip flop. Sometimes it is from the driver's seat and sometimes standing in from of the car looking to the rear of the car. Which "bank" is left and which is right? Is "bank 1" (the passenger's side with number one cylinder) the "left" or the "right"?
Thank you,
Doug