Memorial Day in the United States falls on the last Monday of May.
I figured I could just set a reminder for the last day of May every 12 months, but it doesn't offer "last Monday of May" unless May has 5 Mondays.
This answer doesn't work. I can't set a recurring reminder in the past, because it instead says "recurring reminder created today" as if I created it at the next May, which doesn't have five weeks, so it changes it to "fourth Monday in May" which is wrong, and after that, it doesn't even show up for any subsequent fourth or last Monday's in May for future years!
I also can't select a future May to start the event, because there isn't a May with 5 Mondays again until 2021, which means I would miss two years of reminders.
I thought as a workaround I would go ahead and create the reminder in 2021 to cover that and all subsequent years, and then manually create 2019 and 2020 reminders (although this is not an acceptable general solution, because of the arbitrary number of years ahead you have to go to get a month with 5 of whatever day of the week you are interested in), but when I did that, the reminder still only showed up for 2022 and no years after that!