ESMA yesterday published an updated version of the EMIR Questions and Answers document, which can be found here. The updated question is TR11b on page 85 and relates to the reporting deadline under EMIR Article 9, which is defined as being by the end of the “next working day”.
The answer states that “working day” is defined as the one where the counterparty is located. Thus, if two counterparties who trade bilaterally are in different member states, they would have different reporting deadlines.
It should be noted that in general under EMIR, delegation of reporting responsibility is not permitted. As a result, if a counterparty in one country delegates reporting to one in another, it is not clear whose “working day” is taken into consideration. EMIR REFIT recently introduced an exemption to the “delegation of responsibility” rule when an NFC- trades with an FC (see here).