Needn’t have done vs didn’t need to do

Neednt have done vs didn’t need to do

1. I needn’t have attended the meeting.
2. I didn’t need to attend the meeting.

 

Didn’t need to vs needn’t have done

• Sentence 1 means that I attended the meeting while it wasn’t necessary. The thing is, I didn’t know that it was unnecessary to go to the meeting. Maybe I regret it.
• Sentence 2 indicates that I didn’t attend the meeting because I knew it was unnecessary.

Take a look at the difference between Stop doing sth and stop to do sth