When you scale a region of keys, you speed up or slow down the animation within it. The keys within the region adjust proportionally to accommodate the new size. Increasing the region's size slows down the animation by increasing the number of frames between keys, while reducing the region's size speeds up the animation by decreasing the number of frames between keys.
You can do overall scaling of animation using the Sequence commands in the Animation menu (see Scaling, Offsetting, or Retiming Fcurve Animation) or using the dopesheet (see Scaling Regions of Keys).
If you want to scale all the animation in a scene, branch-select the scene root. This displays all keys for all animated objects in the timeline which you can then resize using a region.
Make sure that Ripple is on or off, depending on what you want to do (see below).
Right-click in the timeline and activate Scale and Translate.
To scale with or without rippling
You can scale the keys with or without moving the other keys on the timeline, depending on whether Ripple is on or off.
To scale the region and push other keys to the right (forward in time), right-click in the timeline and turn the Ripple command on. If you shrink the region (scale down), the keys outside it are "pulled" toward the region.
Drag the region's edge to scale it and push keys with rippling on.
This region is scaled forward by 6 frames and pushes the other keys ahead by 6 frames, keeping the same frame offset between the region and the other keys.
With Ripple on, you can also scale a region that has no keys in it (an empty region) and have it affect the other keys on the timeline. This is useful for easily shifting keys in long animations.
To scale a region without changing keys outside the region, right-click in the timeline and turn the Ripple command off. If you scale the region over existing keys in the timeline, the existing keys are overwritten.
