I just bought this unit and I figured the simplest function would be setting the temp and time. I could not figure out why it was screwing up every time. Did anyone test this before it shipped? That is a big flaw.
The simplest fix would be to make you hold down the button for 3 seconds to get the clock icon. If you hold it for 8 seconds it should toggles C to F or F to C.
What I would do is change the firmware so the clock icon always shows. When you press it you can changes between set temp and set time. If you want to toggle C to F and F to C you hold the start button down for 3 seconds. Far more intuitive then the way it works now. I would also make it so if you hold the clock icon down for 3 seconds it toggles between time and temp every 4 seconds. If you press it once it toggles and keeps the current setting (current temp or current time).