Cardiac pacing is performed using leadless pacemakers (LPs). An AV delay is determined based on a P-wave duration. When pacing occurs during cardiac cycles starting with intrinsic atrial events, the AV delay is set to the P-wave duration plus a first offset if the P-wave duration is greater than a first threshold duration, and the AV delay is set to the P-wave duration plus a second offset that is greater than the first offset, if the P-wave duration is less than the first threshold duration. When pacing occurs during cardiac cycles starting with paced atrial events, the AV delay is set to the P-wave duration plus a third offset, if the P-wave duration is greater than a second threshold duration, or is set to the P-wave duration plus a fourth offset that is greater than the third offset, if the P-wave duration is less than the second threshold duration.