Excel stopped formatting dates

My Excel just stopped formatting dates. Even if I select the column and use the format cells command again it does not work. I recently changed windows language from portuguese to english, maybe this has an influence. I submitted this post before, but I am submitting it again, because I noticed that it happens only on the Date formatting. I am atteching one file, first column is a date. I am an university professor and use this command a lot to change dates into numbers to grade students by their task delivery date. Can someone help?