"This question have been asked before and already has an answer" duplicate of a future post?
14629
Should I vote to close a duplicate question, even though it's much newer, and has more up to date answers?
70613
“possible duplicate” comment should be re-added if it's been deleted
131213
Editing a previous message posts a new one instead
112077
How to check if a value already exists to avoid duplicates?
45986
“community wiki” checkbox in new question shows a dialog twice when self-answering
71646
Duplicates of an outdated question
78555
Double booked - User bookmarking question recorded twice
97874
Notify when my question has been linked from another question
55570
Questions in titles need to be repeated, why?
20899
Linked and Related sections contain duplicate links to questions
133926
What if 2 answers are essentially the same?
18509
Does the new guidance on duplicate questions suggest closing a question as duplicate, if the original answers the OP's question?
134797
Refresh "Questions that may already have your answer" after adding tags based on these tags
142942
"Seen" status is earlier than the user's last post
105704
Question closed as duplicate with  and also shown as "Possible duplicate"
10353
Duplicate flag lists "you have already raised this flag" after flagging as "Unclear what you're asking"
7959
Timestamp on question is later than Profile's Seen, must be some time traveller or ninja