I'm always late, I think I have ADHD, although not diagnosed. (on a waiting list, but always score 'extremely likely' in all the pre-tests).
I mainly forget how long things such as putting on shoes/getting into the car/making sure we have everything we need, going for a final wee takes. I drive my husband mad.
In my single days, my friends got used to me and would tell me 45 minutes before the actual time, however, on the rare occasions I was early, I never used to mind waiting, I realised it was a major, irritating flaw of mine and was grateful to my friends for putting up with me.
I am slowly getting better than I used to be, due to my dh's influence and organisation. having children has also hero somewhat as I really don't want my behaviour to impact them.
Interestingly here is a conversation I had with my friend the other day when she was booking an event I had booked:
Her- Did you book the 2;20 or 2:40 slot?
Me - 2:40, that way, I will have 2:30 in my head and I won't be late. Does that make sense?
Her - not to me! I'll be there for 2 either way!
It bought me up a bit that someone would plan to get there 20 minutes early for something, but when I actually think about it, it makes perfect sense. I can see that by arriving 10 minutes early, I have not planned for getting everyone out the car, coats on (it's a Christmas thing), getting from the car park to the place, booking in etc.
I should probably point out that I am nearly 50, and this is the first time it has sunk in. This is what I mean by "I am getting better' it's just taking a loooong time to learn. 😁
However it is not down to arrogance, rudeness or 'me thinking my time is more important than others' as has been suggested in previous discussions on this topic, I think its down to an inability to see the bigger picture, which I appreciate makes me narrow-minded/thoughtless in this way, but I hope I make up for it in other ways to my friends and family.