The guidelines say, regarding the Release Information:
Use the dates for the first release schedule. If it was released at a film festival, use that date as not to restrict the ability to mark the title as finished for people who watched it at the festival.
In other words, if I've understood the guidelines correctly, the date should be that on which the movie in question was/will be shown to the public for the first time, whether that's at a festival, at a self-contained public premiere event or if it went direct to national release (not work-in-progress nor non-public focus-group or market screenings).
However, most people just browsing and not editing MDL have not read the guidelines. When they see Release Date, they think it means the national release in the main country of origin. When the date is a long time before the national release, this confuses them: I know because I read a lot of comments expressing this confusion.
Therefore, I think it would alleviate some confusion if Release Date were renamed Premiere, since the latter more accurately and unambiguously describes what the date is of.
If I've understood it correctly, I think the guideline on this issue would also be clearer if it was reworded as:
Use the dates for the first release schedule. If a movie was first played to the public at a film festival or its own premiere event, use the date of that screening, so as not to restrict the ability to mark the title as finished for people who watched it at the premiere or a later preview screening. (Work-in-progress screenings, even if open to the public, and any invite-only screenings for focus groups or potential buyers do not count.)
