Canonization refers to placing an individual into the accepted lists of saints. This was first done by placing them on the calendar. It overlaps with a time when many people were added to the calendar to be remembered, but the designation of holy came to be applied to a particular way of remembering. If you know of a saint that is not associated with a particular day, I would love to hear about it!
The Roman Martyrology was originally the calendar of Rome. Other places have their own martyrologies, calendars, ordos.
Eastern Catholics have saints that overlap with the Orthodox, as well as some different from the Orthodox. (St Josaphat, who led a group to reunite with Rome, for example)