The match will be supported by Heineken, current sponsors of Ulster Rugby, who will also be providing a drinks reception at the Gala Anniversary Dinner taking place that evening at the Clandeboye Lodge.
Former Bangor, Ulster, Ireland and British & Irish Lions player Milliken has confirmed his Lions centre partner and life long friend McGeechan will be the guest of honour at the Gala Anniversary Dinner.
"IIan had no hesitation in accepting my invitation to join Bangor RFC for our 125th anniversary," he said.
"He is still heavily involved in rugby with his Bath commitments, but holds his rugby relationships very close to him and was delighted to be able to support Bangor RFC."
Bangor Club President Harry Williams, coach of the 1999 European Cup-winning Ulster team, co-ordinated the support of his former Ulster players, and will coach the team again on the day.
"It is great that we can get the team back together and I look forward to watching players like Stephen McKinty and Gary Longwell roll back the years when they take on the Bangor firsts."
There will be plenty of after dinner entertainment, including Sky Sports pundit and former Ulster, Ireland and Lions winger Tyrone Howe hosting a Q&A with Sir Ian McGeechan in front of the guests.
For further information on Bangor RFC's 125th anniversary, please visit www.bangorrfc.co.uk.
