My friend "Carrie" and I work for the same large organisation (but in different teams). We are white collar, salaried workers. This organisation is pretty flexible in terms of working hours. You can work your (approximately) eight hours a day anytime between 7am and 7pm. This means that if you want to have your working day from 8am - 4pm, or 10am - 6pm, you're allowed to. That said, most people do choose to work between 9am-5pm.
Further, our organisation is pretty easy going when it comes to letting its workers manage their own time. If you've worked from 9am-5.30pm on Thursday, no one cares if you work 9am-4.30pm on Friday (provided you've finished all your work, etc).
Carrie is going on a vacation soon, leaving on Friday 20th. Yesterday, she sent me an email, asking if I wanted to meet for a drink at 5pm on the 20th, noting that she'd have to leave at 5.30pm to catch her bus to the airport.
I replied: "Sounds good, count me in! But how about we leave work a bit earlier, say 4.30pm, so we have time to enjoy our drink."
Carrie wrote back: "[LifeOnPluto], I never leave my desk before 5pm unless I absolutely need to, such as picking up my car from the mechanic before it closes. I am generally expected to work between 9am and 5pm."
I replied: "Our organisation lets us work our hours between 7am and 7pm, so if your supervisor is insisting you work between 9am-5pm every day, they're in the wrong. In any event. I'm sure no one would begrudge you leaving work slightly early on a Friday before you're going on holiday."
Carrie: "Nonetheless, I don't want to leave work before 5pm."
If we only have a 30 minute timeframe, I don't really want to have this drink with Carrie. It will take 10 minutes to walk from our office to the bar, and another 10 minutes to walk from the bar to the bus stop. That only gives us 10 minutes to choose our drinks, order, and bolt them down. I'd much rather relax over a drink, especially on a Friday. In addition, I believe I've been flexible with Carrie in the past (for example, when we've met for a beer, Carrie has said she'd prefer going for a coffee instead. I've agreed, even though I would have liked a beer). But now it feels like she's being inflexible with me.
In addition, there have been a couple of other incidents with Carrie that have frustrated me lately, so that could be colouring my opinion.
My question is: am I on the hook for this drink (after all, I did say "Count me in.")? Or is it ok if I back out of this, and say that that timeframe doesn't work for me?