Please, use your calendar

Literally every phone has a built-in calendar app - your email provider likely hosts one too.

Please use it!

The amount of times I've gone to plan something with someone, and they've agreed to hang out only to cancel last minute because "I forgot it was my grandmas anniversary and my parents are hosting dinner" or something crazy like that.

Calendar events don't need to be super accurate or detailed - they just need to be there. At a quick glance you can see if something is planned for that day.

Apple Calendar is great, Google calendar is great - Apple calendar even lets you add estimated travel time for driving or public transport on the event, so you can better estimate when to leave. I'm not always on time for everything but being able to quickly visualise all this information in an app that's literally preinstalled on most phones is insane and more people need to take advantage of it.

Examples

"Your appointment is at 3:15pm on the Thursday, is that ok for you?"
"That works for me"
"Do you need me to write it on a card for you?"
"No that's ok, thank you"

Put explicit appointments in your calendar as soon as you're told when they are. It'll save the hassle of having to be given a note, follow-up texts, emails, etc.

It's scary how often I've seen people in doctor's offices ask for the time on a note because, "I'm so forgetful!". Please... use your calendar...

"Hey are you free for dinner at Rigo's on the 19th?"
"Yeah"

You didn't get an explicit time - the plan is probably still a bit up in the air. Create an event around 7pm (or whenever you feel is kinda accurate) and add travel time from wherever you think you'll be to the events' location.

As the event gets closer try to follow up with more details and slowly update your event to be more accurate. Having an event there at least lets you know you've got something on in the afternoon.

Now if someone asks you "Hey do you want to come watch a movie on the 19th?" you can decline knowing that it'll probably overlap with the dinner plans - or, you can try to solidify the plans to slot the movie in. All depends on how much effort you want to try to put in.

Wrapping up

Over-estimate, over-plan, always make events worst-case-scenario long. You don't want to stretch yourself thin and end up being that person who's planned every minute of your day down. Keep it simple, round to the hour, whatever works best for you.

It makes shit so much easier to know what's up during your week, when you can just relax because you know nothing's on that day. It's great. I haven't even gotten into how insane it is to share a calendar with your partner or friends for common events - literally everyone with an email account has a calendar.