Start playing the timeline or Animation palette

Spacebar

Spacebar

Switch between timecode and frame numbers (current time view)

Alt + click the current-time display in the upper-left corner of the timeline.

Option + click the current-time display in the upper-left corner of the timeline.

Expand and collapse list of layers

Alt + click

Option + click on list triangles

Jump to the next/previous whole second in timeline (during playback)

Hold down the Shift key when clicking the Next/Previous Frame buttons (on either side of the Play button).

Hold down the Shift key when clicking the Next/Previous Frame buttons (on either side of the Play button)

Increase playback speed

Hold down the Shift key while dragging the current time.

Hold down the Shift key while dragging the current time.

Decrease playback speed

Hold down the Control key while dragging the current time.

Hold down the Command key while dragging the current time.

Snap an object (keyframe, the current time, layer in point, and so on) to the nearest object in timeline

Shift-drag

Shift-drag

Scale (evenly distribute to condensed or extended length) a selected group of multiple keyframes

Alt-drag (first or last keyframe in the selection)

Option-drag (first or last keyframe in the group)