Unix ext2 superblock - file system creation date

I am trying to find the creation date on an _ext2_ file system. I seem to get a current date using dumpe2fs.
The problem is that the original _ext2_ superblock specification does not contain such information, though it seems like there might be an extension to the original fields (something about after byte 264).
In fact using hexdump on the superblock (hexdump -s 1024 -n 1024 -C /dev/vdb) I can find 4 bytes starting from byte _265_ that containg a hex number which contain in little endian the unix time of the file system creation. Any information on how, why and under what circumstances that it there?
Thanks in advance