Eurocopter Technician reported installing tail rotor retaining bolts incorrectly during bearing replacement. The bolts were reinstalled correctly after a routine inspection discovered the discrepancy.

Narrative

On Date; the tail rotor laminated half-shell bearings were replaced on Aircraft X. The tail rotor was presented for CYA (angle of attack system) for assembly and I failed to notice that the bolts were installed incorrectly at this time. Later that same day the tail rotor was installed on the aircraft and I performed the Required Inspection Item for installation of the tail rotor. Ground runs and vibration checks were performed with normal results and the aircraft was returned to service. No mention of abnormal behavior or vibration was reported by the pilots an any time. On Date 1 the off going night shift pilot asked me if the bolts were installed correctly. I told him that I would have to double check the manual; but a quick look at an adjacent aircraft revealed that they were installed the same way on that aircraft. I then went and checked the manual and discovered that the bolts were installed incorrectly on both aircraft. I immediately informed Name and removed the aircraft from service. We removed the tail rotors from both aircraft; removed and reinstalled the bolts in the correct orientation; inspected spherical thrust bearings and reinstalled the tail rotors. Vibration checks were normal and the aircraft were returned to service.Suggestions - Ensure AMTs and pilots are made aware of the correct orientation of the through bolts. Perhaps a note or caution in the Aircraft Maintenance manual to be sure and install bolts in the correct orientation.