Your question and responses in the thread indicate you share a common
misconception of just what a milestone is. It is NOT a certain designated
date. A milestone is an EVENT that occurs during the course of the project
marking an important transition point. Maybe you finish the prototype and
then decide whether to go into production or you get an approval for a
proposal or you finish the foundation of a new building and are ready to
start the construction. It usually marks the completion of a key
deliverable or a signifigant decision point. The event takes place on a
certain date, true, but the milestone is the event itself, not the date on
which it happens. And since it is an event whose occurance depends on the
length of time it takes to do all the things leading up to it, its date will
change depending on the timing of the tasks ahead of it. If it we think it
will take us 6 weeks to lay the foundation, the "foundation ready" milestone
will be shown in the plan as taking place in 6 weeks. If it turns out it
only takes us 2 weeks to do all the things required to complete the
foundation, then the "foundation ready" milestone will move up in synchrony
with the end of that sequence of tasks and take place in 2 weeks. It's true
that most of the time a milestone will need to be reached by a certain date
and that's when the deadline entry comes into play. The date shown for the
milestone is the date you will cross that threshold if everything goes as
you've outlined it. The deadline for the milestone is the date by which you
need cross that threshold. Hopefully the former is earlier than the
latter - if not, adjust the plan of the tasks leading to it until it is.
