My best days are generally more like best weekends. I think I would have to go with the weekend we got engaged.
We had JUST gotten back together after an 18 month separation and I was my moving lovelorn self across the country to Seattle. We had three weeks together in MN, then I was gone. A month later (and two airplane visits) he moved out there to join me. The weekend he flew out we went to a Bed and Breakfast in Victoria BC to celebrate our togetherness. Getting married was a mutual decision, so I knew the engagement was happening that weekend.
Needless to say, it was a beautiful ferry ride, a gorgeous B&B and we had a blast exploring the city and the harbor. It was our first real step forward in life together. We don’t do a lot of romantic stuff, so this one was pretty awesome.