Does my ADR window open on date of first meal, or check-in?

[U2_rocks!]

I've never stayed on site without an ADR for the first night, so I've never encountered this. We check in on Oct 16 to BCV, but first planned ADR will be Oct 17. Do we call 180 days before Oct 16, or Oct 17th?

ETA: we will probably be a Grand Gathering, if that makes any difference, with our group size at many meals being 12.

 

[djp0630]

Check-in.

 

[Shula]

call at 180 days prior to check in and you can make ADRs for your whole trip.

 

[U2_rocks!]

So it's only if you're offsite that you have to call 180 days before each day of your vacation that you have ADRs planned for (or call 180 days before the LAST day's meals if you only want to have to make one call)? For onsite it's based on check-in date instead of meal date?