You are expected at Xero to come in do your best work. The company has a huge focus on balance, that you bring your whole self to work, and work flexible around your life.
We are not forced to work 9-5. I frequently take breaks when I feel like I would benefit from letting myself relax a bit. There are a lot of collaboration and teamwork in each team so the exact work hours will depend on the team.
I've never had anybody question the hours that I work. For developers, I get a sense that output is valued over hours.
I generally work the standard 9-5, but it isn't always fixed. I will sometimes spend a little bit of extra time at the end of the day finishing up a piece of work if it feels like it is something I can cleanly finish off. Generally the work hours are flexible enough that if you need to take a break and work later or earlier in the day you can do so. The main thing would be to try and make any team meetings and being free to communicate with team members.
Most teams are 9-5, for a 7.6hr work day. The company is very flexible with work hours, but basically it depends on your team.