Why am I seeing ##### in the dates columns even though it shows properly before I export it?

 CSV files contain raw data, so when you open them, the columns have a fixed width initially. When spreadsheet programs can't display the full date because the column width is too short, they display the dates with the # sign. In order to view the dates, double click the right border of the column header. This will resize the column so you can view the full date.