The first record in every variable structure file is a system record called the file
header. This is normally 128 bytes in length. 

For an index file, eight bytes into the header record is the creation date and time
entry. This entry is 14 bytes long and has the format YMMDDHHMMSSCC 

This is documented at:

http://supportline.microfocus.com/Documentation/books/sx51/rhfile05.htm