When is this useful?
It is useful before APIs or imports that expect a consistent date format. A value such as 03/04/2026 should not be guessed without knowing whether the source means March 4 or April 3.
Free web tool
Normalize a CSV date column to YYYY-MM-DD and report rows that could not be converted.
Use this to normalize one date column to YYYY-MM-DD when you already know the source convention: YMD, MDY, or DMY. It deliberately avoids guessing a different format for each row.
It is useful before APIs or imports that expect a consistent date format. A value such as 03/04/2026 should not be guessed without knowing whether the source means March 4 or April 3.
One selected input convention is applied to the whole column. The tool does not “pick whichever format works” for each row. That is intentional: unchanged rows can reveal that the source column mixes conventions.
YYYY/MM/DD and YYYY-MM-DD, including one-digit month/day.2026/02/30 stay unchanged.For US-style input, choose MDY. 9/2/2026 becomes 2026-09-02. If 31/12/2026 appears in the same column, it remains unchanged—an immediate clue that formats may be mixed.
“Normalized” means the value matched the selected format and formed a real calendar date. “Unchanged” can mean a different format or an impossible date. Treat unchanged rows as evidence to investigate, not rows to silently discard.