I have not personally done this, but at my last job, one of my coworkers did. She worked full-time our first year working together, but she had 3 young kids and the after-care costs were prohibitive. She wanted to go part-time, but still work 5 days/week. She proposed leaving early every day, and at first got some resistance b/c things just weren't done that way. We worked in a school, and there were concerns she wouldn't be able to see students in the afternoon. I was happy to take the afternoon students, and she balanced it with more students in the morning. We worked that out before she even approached the higher-ups. B/c of our job there were multiple people who had to agree, which was annoying, but luckily most of them were so disinterested they didn't care what we did as long as it didn't create more work for them.
There was some concern that others would want a similar schedule, but I don't know why - it would only make employees happier! Plus, I don't know anyone else who proposed a schedule like hers.
I'd go to your employer with a plan for how it will minimize disruption in the office. Any objections you can foresee, such as it creating more work for others, try to work out yourself (if possible). Basically, make it easy for them to say yes and hard to say no. Good luck!