Hi!
This has always been an issue for us. I beleive the right one is MM-DD-YYYY, however in the CSV uploader you can select the format. This is what is stated in support page

• Date/Time Format: Determine the date/time format of the whole data file. If you exported the file from Qualtrics, the importer will try to detect the timezone you set on your account at the time the file was exported.

Same as ana_velez_voce I have always been struggling with this... I am using the highlighted format:
The funny thing is that I set the date in this format in a csv file, save and do not close the file. For some reason if I close it before uploading, the date format goes completely wrong

I used to follow the format yyyy-mm-dd HHss and its works well for me however, in some cases to getting the date in this format is a complex task. I usually try saving the csv file in csv UTF-8 format so that it retains the format even after we close the csv file.

Thanks so much everybody on this thread as well as TomG . All of your suggestions were very helpful. Here is what I found that worked best for this issue:
PraDeepKotian_Ugam 's UTF-8 suggestion was key for this. Also TomG recently recommended the date optioned field ${date://CurrentDate/c}. This was important because when it comes to reporting it recognizes the timezone correctly. ${date://CurrentDate/DS} works as well, but didn't adjust the timezone. Here was the main thing for me. When looking at the dates in Data & Analysis it will just show the date "Oct 6, 2020" without a timestamp but if you want to use this in reporting or on export, whenever I added that it gave me the correct timestamp as is shown like in Start Date, End Date, Recorded Date which is also filterable. ${date://CurrentDate/DS} didn't adjust the timezone. The drawback is if you want to filter by timestamp in Data and Analysis but at least you get a filterable field. Thanks again everybody!