Blake’s Universal Rule of the Universe #75
75. If someone is basing their plans on your availability, and that availability changes, TELL THEM. Or don’t be mad when you show up three hour late and they’ve eaten your dinner and are waiting to hit you in the genitals with a baseball bat.
Read the rest of the Universal Rules of the Universe right here!
Evertime Realms 
Just a quick, FYI. The title correctly lists this as the 75th universal rule, however the first line of the post labels it as the 74th.
Thanks for the heads-up. Fixed.