The baseline doesn't get automatically updated - that's the whole idea of a
baseline. When you have completed planning and are about to start work, you
save the baseline. This takes a "snapshot" that locks down and preserves
your original plan. Now when you enter actual progress into the plan you'll
find start and end dates for the tasks you've worked and their dependents
change to reflect the actuals you have obtained. But the *baseline* OTOH
does *not* update , thus giving you a constant reference against which you
can compare the project as it currently stands against what you thought
you'd have by this date, giving you variances etc to determine if you're
running ahead or behind schedule and over or under budget.