Move all symbols on a row back by the same amount of time

Question:

I have 30 milestones on a row. I am looking for a way to move the dates of all milestones at once. That is, I want to move the first milestone back three weeks and want all the milestones to the right of it to move back also. Is there a way to do this without changing each individual date?

Answer:

Method #1: Turn on "Dependency Mode":

Turn on Dependency Mode:
Move the first symbol on the row with your mouse and symbols which fall after the symbol on the task row will move by the same amount of time.

Method #2: Shift all dates

With the Arrow Tool selected, select the task line.
On the Edit menu, choose Shift Dates for Selected Tasks.
Enter the number of days to shift.
Choose "Backward" since you want to shift the dates backward.
Check on 1 Task Rows are selected....
Press OK.