Has anyone else commented on how slow Excel 365 is?

I have a set of templates and macros that I have built up over the years. They are fast and reliable, minimising the use of volatile functions.

Spreadsheets built with Excel 365 though, and spreadsheets converted to it, take ages to calculate as they tick slowly through the percentage complete. I am using Windows 8.1 on an 8 GB machine with 4 processors.

When I save, however, it does a calculate before save and that zips through the calculation very quickly in the time I would expect of it. However, I can hardly save every time I want to calculate. (Well, I can but I shouldn't have to.) Why is normal calculation not the same speed?