I've set-up 3 data frames with the same data at the same scale and with the same projection. However, I've change the datum on all 3 data frames and have created a graticule (lat & long in degrees) with the same properties and they end up generating the same coordinates at the same locations in all 3 data frames.
My question is: Shouldn't my graticule's be different for each data frame since I have change the datum?
How I understand graticule's is that they are based the the reference Sphere/Ellipsoid that you are using and that is stored in the datum of the Projected coordinate system.
Is my ArcMap Desktop 10.2.2 changing the graticule's to all be the same or am I not properly understanding the concept of a Graticule.
The datum is the spheroid that the graticule is draped on. Your point will still be at xxx Lat and xxx Lon no matter what datum you use, so you will see no shift looking at graticules. The differences come into play when you mix and match datums, then you will see shifting and misalignment.
Randy McGraw to see this in action, create a feature class or shapefile with the Create Fishnet tool and define its geographic coordinate system (GCS) to one of the ones you're interested in. Now use the Project tool to create copies that are in other GCS (including appropriate transformations).