A history lesson required for Gerry?

I don't think I have any readers from Monaghan but if so, then you should get down to the Westenra (spelling? But that's what the Shinners are calling it) Arms Hotel tonight for 7.30pm.

Gerry Adams promises (here and here) to be:

“collating views from a wide spectrum of public and community opinion on the many disadvantages of the border”.

Or, at least from a wide spectrum of "Sinn Féin Mayors and Chairs from across Ulster" and if you're so inclined, you can check out the "photo call of all elected representatives at 7.30pm in the Old Town Hall Function room".

However, one little "fact" in the press release grabbed my attention:

Sinn Féin President Gerry Adams, alongside newly elected TD for Donegal south-west Pearse Doherty, will launch a cross border initiative “Bridging the Border-Reconnecting Communities” at a Uniting Ireland Rally on Monday 29th November in the Westenra Arms Hotel in Monaghan town at 7.30pm on the 90th Anniversary of the partition of Ireland.

I'd be grateful if those with a stronger historical background than myself could confirm this for me...but the 90th Anniversary of the "partition of Ireland" (ie when the Government of Ireland Act came into effect) is surely next year on 3rd May?

Has the excitement of standing in the Republic's forthcoming election got Gerry all muddled-up or is there genuinely another landmark date he could be referring to?