What are "deadlines" all about ?

They are not useful for safety-critical projects.

I conclude they are not useful at all.

A "deadline" ensures that a system with bugs is stamped as correct to meet the deadline. Because the deadline has been met, individuals reason that the development tools can be thrown away.

To mr_220volts_rms,
Thanks. Terrific.

The time something must be done by.

Well you do not argue a convincing case for a safety critical project then, instead for a deadline critical project.
But that does not dissolve the usefulness of a deadline.
A newspaper has deadlines because they print a paper daily.
That means that the stories for that days publication must be done before it goes into print.
But the reason it does not conflict with primary goal is because the goal is to print a paper about the news daily.
A deadline on a safety critical project could potentially compromise the effectiveness of a system to insure safety.
But the idea itself is flawed from the start because safety is based upon the probability of causalities as described in military terminology.
Often the primary goal is mission effectiveness.
So safety critical becomes an almost meaningless goal for a system.

without a deadline, you don't know when things are done, to plan the next step and schedule it. and also if we didn't have dealines, how do you know if it will ever be done?

Well
this is happening everywhere.
But one should be reluctant to these things.
U should at least keep ur part strongly..
rest what happens is all grace of God