I have officers with the latest phone gadgets with all the bells and whistles. They have alarms, reminders and probably self-texting messages. Any technology created by man is susceptible to breaking down. A backup calendar in the locker or on the family bulletin board (refrigerator) may also help. It is not a bad thing for your spouse or significant other to ask you about court either.
A former captain in mine gave pocket calendars every holiday season. You know the ones that look like a checkbook and had the new upcoming year in it. None of us used them, but I asked him why give out calendars? He wanted to give something to his staff that was economical but useful. But also, when he had all of us in a meeting you better had known your schedule. The subliminal message was, "Be there and don't embarrass yourself."
The official reminder was to prepare and schedule your events (range, training and court) and life. Matter of fact, I used to give out calendars myself. Good reminder for all.
My many years of experience with officers reveal that I can usually predict your first discipline incident. You will probably miss court or some other non-reoccurring event and then you're left to explain "why, oh why" to some crusty old sergeant with no sense of humor. You're hard-charging, getting it done on the streets.
Off time becomes precious and you oversleep the alarm for court. Now, you have to explain that there is no explanation. The dog does not eat the subpoena. Take your lumps like a professional, and use it as a learning experience.