In GanttView, timescale is represented by the Timescale class which is accessible through the Timescale property of the Task class. You can use the Timescale property to set tier for timescale to Top Tier, Bottom Tier or Middle Tier.  In addition to, you can also set the format and units for the timescale using the Format and Units property of the ScaleTier class. The Units property takes the TimescaleUnits enumeration to set the unit of timescale.

Below code snippet shows how you can set tier for timescale in the GanttView.

ScaleTier st1 = c1GanttView1.Timescale.TopTier;
    st1.Units = TimescaleUnits.ThirdsOfMonths;
    st1.Format = "sd";
    st1.Visible = true;