The schemes used for referring measurements made using the Parkes observatory clock ("UTC(PKS)") to Universal Coordinated Time (UTC) are as follows: . From MJD 48111 until 50840, the offset between the Parkes clock and the clock at the NASA Deep Space Tracking Station at Tidbinbilla was monitored using a microwave link. ... Beginning on MJD 50844, regular monitoring of the offset between the Mark IV Parkes clock and the time standard of the Global Positioning System (GPS) was performed. ...