Jared Sanberg has an excellent article on the dangers of false deadlines.
In many offices, setting false deadlines has became as chronic as breaking them.
Molecular biologist Christine Martens has had more than her share of deadlines set to an artificially early date. One of her former bosses set a do-or-die deadline of Thursday afternoon for a research summary report. After she met the deadline, she discovered he had taken off both Friday and the following Monday. "Nobody took his deadlines seriously after that," she says.
Another boss, anticipating lateness, routinely moved all deadlines up. "If there are no consequences to being late — because you aren't really late, because the deadline wasn't real — you'll be late again next time," Ms. Martens says. Making matters worse, that boss made everyone use project timeline software, a graphical representation of a project's progress. Ms. Martens updated it weekly but says, "Wasting time on timeline software didn't seem very productive to me, especially if all I had to do was move the little bars around to be in compliance again."
I have fought this problem at every place I've worked. What I've learned is that consequences have to be real, or people ignore them.