Last year I few on December 31st. PVR - YYZ - YOW.
The YYZ - YOW flight was cancelled and I was put on the first flight of 2019 (00:10) - so that credited to 2019. However, an email to Aeroplan solved that are they moved the miles back to 2018.
I'm only saying that in the event that you have IRROPS you do have some recourse to request the miles to be credited back to the previous year.