1) One of your two classmates from a group project has to demo it to the professor at 11am -- you know, the one you three worked on until 11:30pm last night? Your phone rings at 8:35am because he shut his laptop down and can't find your work. It took you so long to fix his laptop last night, there's no talking him through this over the phone.
2) It must be (every other) Friday, because the maids are here an hour early trying to clean around me while I get ready for work.
3) An 8:52am email (you read at 9:35am) invites you to a once a month 9am meeting with your partners in the UK.
Few things make my blood boil at much as #3.