Changing Creation Date of a file
touch -t normally only changes the modification and access times. It only changes the creation time if the target time is before the original creation time.

touch -t 199912312359 file.txt
touch -t $(date -jf %FT%T 1999-12-31T23:59:59 +%Y%m%d%H%M%S) file.txt


SetFile -d always changes the creation time.

SetFile -d '12/31/1999 23:59:59' file.txt
SetFile -d "$(GetFileInfo -m test.txt)" file.txt


SetFile is part of the command line tools package which can be downloaded from developer.apple.com/downloads or from Xcode's preferences.