I purchased an animated model of an opening book originally designed in 3ds Max and have been working on converting it to a COLLADA file for use with Apple SceneKit. I was able to get the vendor of the model to convert it to a Blender file, and theoretically Blender can output .dae.
I noticed that the animation was too long, with a delayed start, and continuing several seconds after the book was open. So I thought the right thing was to use the Dope Sheet to delete the unnecessary keyframes, and then shift the remaining keyframes back towards t=0. But As you can see in this screenshot, even after doing this, the timing of the animation is unchanged: the book is still only partially open when the Timeline scrubber is past the last keyframe.
This is my first time using Blender, so please don't hold back on spelling it out for me (e.g., key shortcuts to perform actions).