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. 
 
Important: The deleted block is not copied to the clipboard. 
Procedures
To delete a block of time:
- In Dope Sheet mode, highlight one or more item labels in the Controller window to specify tracks for time editing. 
 
-  Use 
 (Select Time) to specify a block of time.  
- Click 
 (Delete Time). 3ds Max deletes keys in the specified time block. Any keys to the right of the block move leftward.