Problem Formatting Date Field on Excel for Mac 2011

Afternoon, new to this forum and a moderate Excel user. If this is posted improperly, let me know and I can adjust.

I am running MO 2011, on a macbook pro laptop. I am using Jitterbit dataloader to import a large .csv file into Salesforce. Salesforce needs the date in the format yyyy/mm/dd, but that format is not even an option in my Excel formats. I have tried uploading the csv file into Google Drive, formatting there and then downloading again, but my Excel seems to just change it back. I have also tried changing dates manually, no success. I have a consultant that is stumped, and I am not an expert. Has anyone seen this issue before that can make a suggestion for solving? Don't want to attach the spreadsheet since it has sensitive info, but the date field is my problem issue.

I work for a NP that does a lot of fundraising events, so I know I will see this issue again, any advice or new ideas would be greatly appreciated. Thanks for your help.

Hey Alan,
Thanks for the response and associated pic, all good here on formatting the date now. One more follow up. It seems I can change the format to what I want, save it, and close it for use with Jitterbit. But if I re-open the file it will appear with the date field once again in mm/dd/yy format. Am I understanding correctly that my format changes will remain as long as I don't re-open the file? Thanks for your time! GAVIN