A column of dates from an export, a bank statement or a colleague abroad: is it DD/MM or MM/DD? Looking at one date canβt tell you, but the whole column can. This tests every format against all values, uses impossible days (13+) and chronological order as evidence, and converts everything to unambiguous ISO 8601 (YYYY-MM-DD).
If every date has both numbers β€ 12 and the list isnβt ordered, the format genuinely cannot be determined from the data β the tool says so instead of guessing. Ask the source, or look for another column (such as a weekday) to confirm.