For inherent technical reasons, most asynchronous time measurement systems, such as tapped delay lines and BOUNCE, yield superior resolutions than the synchronous counterparts. However, for high performance systems with a resolution of 10 ps or below, the calibration process is involving, tedious, and error prone. This paper shows that with the integration of another asynchronous phase shift detector, called X-ORCA, the calibration process becomes more reliable and surprisingly easy.