Excel keeps changing “January 2026” into “JAN-26”. How can I force it to display “January 2026”?

Hello,

Thank you for your reply. I did what you told me to do even before your message but it didn't work. I have tried again but it still doesn't work.

Look at the picture below. I think there is another issue but I don't know what to do.

Thanks in advance for your help.