Timetable discrepancies

[Padna]

Can anyone explain why the Irish Rail and Translink timetables are not in agreement for several of the Entreprise services?

For example, on the first service each weekday from Belfast to Dublin, Irish Rail shows the intermediate station times as 0717 (Portadown), 0739 (Newry), 0757 (Dundalk) and 0820 (Drogheda). But Translink shows 0721 (Portadown), 0742 (Newry), 0800 (Dundalk) and 0821 (Drogheda).

There are several other differences as well (up to 5 minutes in some cases). I wonder which times are correct?

It doesn't inspire one's confidence in the service (and the prosepects for its badly needed future development) when the two companies involved can't even agree on the timetable.