Take a look at the DATETIME_FORMAT() and DATETIME_PARSE() functions. Depending on your data source and process flow, you may need to use two fields, one to import as a text string and the other to convert to a datetime value (or vice-versa). In either case, you’ll use a format specifier to define how you want to read or output a date string.
Also keep in mind the ‘Use time field’/‘Use GMT’ toggles can be destructive, so don’t go flipping them randomly. They define how data is stored; they aren’t mere formatting options. If you change a time field setting and want to change it back, it’s best to ‘undo’ rather than simply flip the toggle again. (While figuring out how to configure dates when using live data, I usually duplicate the field in question, keeping an untouched version as backup.)
