Why are the dates in the Z-trains file out by 44 years ?

‘Z trains’ buses, ships, and trains are manually input by our service supplier so that services which are not supplied by Network Rail in the CIF data are in the timetable data supplied to retail users.

‘Z trains’ have to be input in a very old format, which is designed to cope with pre and post-Year 2000 dates, which is why at first sight they appear in the output data as appearing to run in 2055-56.

The date translation for Z trains is to subtract 44 i.e. a date string “550108” means 8 January 2011.