A calendar or agenda is not only a tool to remind us to do things, but to help us take control of our life. You see, many people react to events instead of planning for things to happen.
As a pastor, I need to learn be in control of my time and life, otherwise, things will get out of hands. There are meetings, pastoral visits, church services, personal appointments and family time that need attention and if I don't do so, chaos will reign. (Just ask my wife how many times I had to cancel a date with her because I had a meeting I forgot about).
To avoid conflict and me sleeping on the couch, my wife and I share a Family Calendar so we both know what's going on and don't schedule something else. We also have access to our Church's Calendar so everything is connected.
We both use Google Calendar and Apple Calendar and made sure everything is synchronized, so no matter if we use our phones or computers, everything will show up in our calendars.
There is power in being able to take Control of your agenda and being able to say no. Don't let things happen to you, but make things happen.
"But let your ‘Yes’ be ‘Yes,’ and your ‘No,’ ‘No.’ " Matthew 5: 37 NKJV