Use the Edit Time tools to work directly with selected blocks of time in the Dope Sheet Editor, as opposed to working with keys and range bars. A block of time is any contiguous time segment, across one or more tracks, and is independent of key locations.
Enter Edit Time mode by selecting a time segment in the Dope Sheet Editor. Once a time segment has been selected you can insert, cut, copy, paste, and reverse the time segment, including its keys. You can also scale and insert blocks of time. The time tools are available from the Time menu and the Time toolbar. Time tools are unavailable from the Time menu in Edit Ranges mode.
In Edit Time mode, keys and range bars of your animation are there only for reference. You select blocks of time and then apply time-editing functions to your selection.
Select the animated object, then right-click and choose Dope Sheet.
This opens Track View with the Hierarchy window showing the animated object.
(Edit Keys) isn't highlighted on the Keys Toolbar, click it to activate it.
(Select Time) or from the Time menu, choose Select.
With Select Time you can specify a block of time by dragging in the Key window.
Use Delete Time to delete a selected block of time and any keys inside the selected block. Keys to the right of the deleted time move to the left.
Use Cut Time to delete a block of time from one or more tracks and place it in the clipboard. Before you can paste time in a track, you must have time in the clipboard. After specifying a block of time, place it in the clipboard with Cut Time or Copy Time.
Use Copy Time to copy a block of time from one or more tracks to the clipboard, after which you can paste it to other tracks.
Use Paste Time to paste a block of time from the clipboard into one or more tracks.
Reverse Time flips the order of keys within the selected time. You can reverse time by scaling a selection past its left edge, but this also changes the position of the selection and the remaining keys around it. Use Reverse Time to reverse keys within a designated block of time.
Use Insert Time to interpose time into highlighted tracks. Inserting time adds time at a selected point in your animation, making existing keys slide out of the way.
Scale Time scales a block of time. You can scale down to fit into less time, or expand it to fill more time. Scale Time doesn't use the Track View time slider as the scale origin reference; it always scales from the first frame of the key selection.
Use Exclude Left End Point to exclude the beginning key in a selected block of time.
If you paste the same block of time repeatedly, one block following the other, you can create a looping segment in your animation. To create a smooth looping animation, you need to exclude either the first or last key of the copied block to prevent keys from doubling up at the ends.
(Edit Ranges) is active instead.