1. Select an object.
2. Click Animate in the main tool palette.
3. Click Invert Keys in the lower tool palette.
4. Enter a frame range. To alter all objects in a scene, enable the All objects option. Click OK to accept or click Cancel to abort.
5. All keyframes for the current object, or all objects, between the inpoint and the outpoint will be inverted.

Frame range - Defines a range of frames which this function will effect.
Centered on - Defines a pivot point around which the keyframes will be flipped.
All objects - When enabled, forces the function to effect all objects in a scene.