...I have the same, um, situation with my wife.
Update: A few years ago, I established this ground rule with my wife. Since she doesn't do Calendars and Time/Day management very well, I reserve the right to not go to Any family/work/important event not planned in advance, when it is in conflict with a paying
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My wife finally got calendars/time-day management together after many years of double booking/canceling/missing appointments and many other faux paux regarding scheduling. We found a home calendar with a front pocket for each month that can store medical appointment paper work, maps, game schedules and such. She also keeps her cell phone calendar up to date.
Still, the basic rule is, neither of us can schedule anything regarding family without checking with each other first and checking the calendar for conflicts. Best thing she learned was to replay to every invitation with "I need to check my calendar and with hubby before I can confirm". Not that I control her or anything like that, just out of respect. I do the same for her.

We've been together for a long time so there's no drama involved here, just an attempt to rein in the drama that can surround family scheduling.
She usually texts me with any possible upcoming events or changes in scheduling so I can see how they will work into my schedule. I'm usually involved with home projects, practicing, home maintenance and other stuff, this helps me out a lot.
Since most scheduling decisions don't need to be made quickly, this has worked very well. That way, if we agree, she can schedule family events around whatever I'm doing so I can attend. She can also elect to attend them by herself if there's a conflict. I like to attend only about one or two family events per month (due to my hobbies and my personal time) I chose to stay home many times anyways.
One other thing we do is to, if at all possible, not schedule more than one event per day. Too many things happen along the way and there always seems to be a seem kind of problem that happens before or after each event that get in the way. We decline many events do to this rule.
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