You can manage time in the Dope Sheet using the Select Keyframe Tool. With the Select Keyframe Tool, you can place and create the Dope Sheet Manipulator. The Dope Sheet Manipulator lets you select, move and scale, as well as copy, cut and paste blank regions of time and regions of time that contain keys in the Dope Sheet. This is useful when you want to move, scale, mute, add or delete regions of time and keyframes and have the rest of your animation shift to accommodate the addition or removal of time and keyframes. For example, when a region of time and keys are cut, the rest of the time and keys in the animation will shift to fill in the gap created by the cut. When the time and keys are then pasted, the animation will shift to make room for the pasted time and keys.
This tool lets you quickly manipulate individual keys and tangents with a single mouse action.
This tool differs from the Move Tool in that it will only operate on one key at a time. It will also operate on the closest selected key of an active curve without you having to precisely select a key point or tangent handle in the graph view.
Choose the Insert Keys Tool to place new keys on an existing animation curve. To select the curve you want to add a new key to, click the curve.
The location of the new key is determined by 
-dragging along the animation curve. The key is placed when you release the mouse button.
The new key will possess tangents that preserve the original animation curve segment’s shape.
The Add Keys Tool lets you add keys to a selected animation curve anywhere in the graph view.
-click the location on the curve where you want to place the new key. Releasing the mouse button places the key.
The new key’s tangents will be of the same type as the adjacent keys’ types.
The Add Keys Tool places a new key on the curve at the time where you -clicked. It works like the Add Keys tool in the Graph Editor with an important exception. Because the Dope Sheet view area does not display values, using the Add Key tool in this window results in keys being placed with their value set to the current value of the attribute.
The Stats fields numerically represents a selected key’s time and value. You can edit them explicitly by entering values from the keyboard, or relatively by incorporating operators into the input. These operators are the same as those employed in the Channel Box. For more information, see the Basics guide.
Center the view about the current time
This icon centers the current time in the Dope Sheet’s view area.
This button toggles the Hierarchy Below option available in the List menu. See Hierarchy Below for more information.
This button toggles the Auto Load Selected Objects option from the List menu. See Auto Load Selected Objects for more information.
This button loads selected objects into the Dope Sheet View Area when Auto Load Selected Objects is not enabled. See Load Selected Objects for more information.
