I had a tricky issue with importing data containing dates in a csv file. When I enter or paste the date value into the csv file it formats it as a date data type but gives it the default formatting, in this case like this: 10/3/2020. But when importing into TG this format is not recognized as valid data and defaults to 1970-01-01.
OK, so I converted that column in the csv file to text and input it as 2020-10-03. Saved the file, reopened it later to change a column header, resaved, closed and imported it. Same problem occurred - 1970-01-01. Not believing my eyes\process I repeated several times until I discovered that if I carefully save the file with the proper format and NEVER reopen it, in most cases the date values imported correctly. Reopening the csv file automatically converts dates back to m\d\yyyy format.
So I think this will be problematic but I also understand that you have a problem taking different date formats as 10/3/2020 could be Oct. 3, 2020 in one culture and Mar. 10 2020 in another culture. I don’t know what the answer is for this other than adding big red warning signs in the docs and Graph Studio regarding the dangers of csv files and dates. Good luck on this one.