Mac OS change creation and last modification dates of a folder
I believe following find/touch should work:
find /target/dir -exec touch '{}' \;
From man touch:
touch -- change file access and modification times
I am not sure whether this is problem with Mavericks or what, but touch -mt OR touch -t just update the modified and last opened time.
Maybe touch -mt OR touch -t commands are working with 10.8.4 and earlier.
For Mavericks, I found solution as below.
SetFile -d '12/31/1999 23:59:59' file.txt
MM dd yyyy hh mm ss fileName
To update all files in folder just use
SetFile -d '12/31/1999 23:59:59' *