It looks like they are rolling it out in stages. I have Excel for Mac on two devices. One has it already, the other one not yet. It's also marked as "BETA". On

It looks like they are rolling it out in stages. I have Excel for Mac on two devices. One has it already, the other one not yet. It's also marked as "BETA". On macOS you can find it in Preferences and then in the "Edit" category. I'm glad they finally introduced this option. Unfortunately the previous behavior is still the default. If someone sends you data and does not know about this, your data will still be subject to the old conversion rules.