I think you can also scale the timing of keyframes without going to the curve editor. Try right-clicking on the timeline underneath your viewports and choose Configure. Then pick "Show Selection Range", and an additional space will open up below your timeline. If you select several keys of your animation now, a bar with two endpoints will span from your first to your last selected keyframe. Grab one of the endpoints and scale away!
I think Max defaults to snapping to the nearest frame, so you won't have to worry about keys ending up on subframes unless you want to. I was so glad to find this a few weeks ago