photo sort order

[dmz]

I have searched and read about photo sort order but cant quite find the detail I am after. One statement i found said the photos are stored in chronological order but there are many dates to choose from. Does it use the file creation date or does it use one of the EXIF dates or something else? From my experience it does not use the "date photo taken" EXIF field which is a pity cause i wouldve thought that was the best option.
Thanks

[dmz]

After experimenting with my new colour ipod I have discovered that the order in which photos are kept is ascending order of the filename. So I use a vbscript to rename the files after they have downloaded from the camera in a yymmddxx format and now have the order on the ipod that i wanted.