Why was it Microsoft 365 in the first place? Does it not work on leap days ?

Good question, 360 would have been better, full circle coverage of all your (office) productivity needs.

Then the next version would have been Microsoft One.

Microsoft Series X Copilot

Microsoft Series X Copilot for Business E3 with Copilot

The sad part is that that name doesn't feel like that much of a stretch for Microsoft. I wouldn't put it past them to end up with two products called Copilot.

You mean like GitHub Copilot and Microsoft 365 Copilot?

You only pay fro 365 days a year. The leap day is free.

In 2020 I was disappointed they didn't rename it to Microsoft 366.

The Zune didn't ;p