In Scrum every sprint has the same length and the same set of ceremonies. This regular cadence forms the heartbeat of the team.
Our very first sprint was three weeks, but that felt a bit too long. So we made our second sprint two weeks long. It has remained so ever since. We have toyed with the idea of changing it to one week sprints, but the need was never there to really try it out.
Our sprint starts with the Sprint Planning on Wednesday morning 10:00. It is timeboxed to two hours. In the early days we really needed those two full hours, and I sometimes had to cut the meeting short. Since we are doing backlog refinement more regularly, our Sprint Planning usually doesn't take much longer than a single hour.
Backlog refinement takes place on Mondays 11:30 and takes one hour. There's also a refinement session on Wednesdays 11:30 in the weeks when there's no Sprint Planning. By planning it right before lunch we make sure we keep it to one hour, because by 12:30 everybody wants to go to lunch.
Sometimes we skip these refinement sessions if there's nothing to refine. Sometimes we have an impromptu refinement session if there's a sudden burst of work coming in. All in all, this has proven enough refinement for us to make the Sprint Planning go smoothly.
We have the Sprint Review on Tuesdays at 16:00 and the Sprint Retrospective the next day, Wednesday, at 09:00, before the Sprint Planning. We used to have the Sprint Review at 14:30 and the Retrospective at 16:00. Moving the Sprint Review to the end of the day gave us more time to finish some final stories and prepare for the demo.
Also, at the end of the day we could sometimes be tired and cranky, especially if the Review didn't go so well. That would have a negative effect on the Retrospective. By moving the Retrospective to the next day's morning, everybody would be refreshed by (hopefully) a good night's sleep. This had a positive effect on the Retrospective.
In a sense our Retrospective has become the start of a new Sprint, rather than the end of the old one. By having the Sprint Planning right after the Retrospective, the ideas that are formed during the Retrospective are still fresh in our mind when we set out to plan the next Sprint.
So, that is our Scrum heartbeat. For us this has worked very well. I'm very interested in what your team's Scrum schedule looks like. Feel free to leave a comment!