When reading calibration chevrons during mark-on-belt (MOB) sensor timing calibration, cyan portions or legs of printed chevrons are detected in order to determine a timing window offset adjustment. Depending on which of the six cyan legs on the left side of the chevrons are detected, a determination can be made regarding whether the window needs to be started earlier or later. If only the first two cyan legs on the left side of the chevron are detected, then the MOB sensor timing window is beginning (and ending) too early and an appropriate adjustment can be made to cause the timing window to initiate later. If only the last two cyan legs on the left side of the chevron are detected, then the MOB sensor timing window is beginning (and ending) too late, and appropriate adjustment can be made to cause the timing window to initiate earlier.