Graph Editors menu > Track View - Dope Sheet > Time menu

Use tools on the Time menu to edit, adjust, or reverse time. The Time menu is available only when Track View is in Dope Sheet mode. The commands on the Time menu are available only when Edit Keys is on. If you are using Edit Ranges, these commands will not be accessible. If you are using Edit Keys, once you select a time range, the remainder of the time menu commands will become available for use.

Select—Select a time range.

Insert—Add blank periods of time into a selected range.

Cut—Remove a time selection.

Copy—Copy a time selection. Includes any keys within the time selection

Paste—Duplicates a copied or cut selection.

Reverse—Rearranges the order of keys within a time range, flips time from back to start.