CSV Date Format Converter
Convert a date column between ISO, US (MM/DD/YYYY), EU (DD/MM/YYYY) and slash / dash variants.
Quick answer: Convert a date column between ISO, US (MM/DD/YYYY), EU (DD/MM/YYYY) and slash / dash variants.
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Frequently asked questions
- Why do I need to specify the source format?
- Because `01/02/2026` could mean January 2 (US) or February 1 (EU). We never guess — pick the source format that matches your data and the conversion is unambiguous.
- Which date formats are supported?
- ISO (YYYY-MM-DD), ISO with slashes (YYYY/MM/DD), US slash (MM/DD/YYYY), US dash (MM-DD-YYYY), EU slash (DD/MM/YYYY) and EU dash (DD-MM-YYYY). Both as input and output.
- What happens to rows that don't match the source format?
- They're left as-is and counted as 'unparsed' in the footer. Your downstream system will see the original value — typical when a column has a mix of dates and free-text comments.
- Does it convert datetime values too?
- Right now only the date portion is converted. Embedded times (`2026-05-01T12:00:00`) are not yet supported — strip the time component first if you need pure date conversion.
- Will my CSV be uploaded?
- No. The conversion is 100% client-side using Papaparse and a small pure-JS date helper.
- Can I convert two date columns in one pass?
- Not yet — run the tool twice, picking a different column each time. The output of the first run is the input to the second.
- Why does ISO format matter?
- ISO 8601 (YYYY-MM-DD) sorts lexicographically the same as chronologically — sorted text matches sorted dates. It's the safest format for storage and interchange between systems.
- Will months and days outside 1-12 / 1-31 cause errors?
- We refuse to parse impossible months (`13`) or days (`32`); those cells are flagged as unparsed. Real calendar validation (`Feb 30`) is on our roadmap.
- Can I parse `Jan 15, 2026` style dates?
- Not in this tool yet — month-name parsing is supported only by the underlying loose-date helper. Convert long-form dates to numeric form first, then run this tool.
- Does the rest of the row stay untouched?
- Yes. Only the chosen date column is rewritten; every other column is passed through byte-for-byte.