Normalize mixed date formats in a CSV
Exports from different systems mix 12/31/2024, 31.12.2024 and “December 31, 2024” in the same column. Upload your file and SpreadsheetFix converts every recognisable date to one consistent format, ready for databases, BI tools and imports.
Free up to 5,000 rows · No sign-up · Nothing uploaded
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Before and after
order_id,ordered,shipped 1001,12/31/2024,Jan 2 2025 1002,03/04/2024,March 6 2024 1003,2024-05-01,5 May 2024
order_id,ordered,shipped 1001,2024-12-31,2025-01-02 1002,2024-03-04,2024-03-06 1003,2024-05-01,2024-05-05
How it works
- 1
Upload the CSV or Excel file containing your dates.
- 2
SpreadsheetFix checks each column to work out whether it is month-first (US) or day-first (European).
- 3
Pick the output format — YYYY-MM-DD, DD/MM/YYYY or MM/DD/YYYY — preview the changes and download.
Is 03/04/2024 March or April?
It depends on where the data came from. SpreadsheetFix looks at the whole column: if any value has a day above 12 in the first position (25/12/2024), the column is day-first; if it appears in the second position (12/25/2024), it is month-first. Each column is judged separately, so a US order date and a European delivery date in the same file both convert correctly. If a column gives no evidence either way, SpreadsheetFix reads it day-first, and you can force US or European order in the rule settings.
Formats SpreadsheetFix understands
ISO dates (2024-03-04), slash, dash and dot separated dates (03/04/2024, 03-04-2024, 03.04.2024), and written months in English, full or abbreviated (March 4, 2024; 4 Mar 2024). Cells that aren’t dates are left untouched.
Why use YYYY-MM-DD
ISO 8601 dates sort correctly as text, are unambiguous across countries, and are accepted by virtually every database, spreadsheet and import tool. It’s the safest default when you don’t know where a file is going next.
Frequently asked questions
How do I change the date format in a CSV file?
Upload the file above, choose your target format in the Normalize Dates rule, and download the result. Every recognisable date in the file is rewritten to that one format.
Will it confuse US and European dates?
SpreadsheetFix infers the order per column from values that can only be read one way, such as 25/12/2024. If a column is entirely ambiguous, you can set US (MM/DD) or European (DD/MM) order explicitly.
Why does Excel change my CSV dates?
Excel guesses date formats from your computer’s regional settings when it opens a CSV, which can silently swap day and month. Normalising to YYYY-MM-DD before opening the file avoids that guesswork.
Are non-date values affected?
No. Only cells that parse as valid dates are changed, and every change is recorded in the change log.
Is date normalization free?
Yes, for files up to 5,000 rows. Pro raises the limit to 500,000 rows and adds Excel export.
Cleaning bigger files every week?
Pro cleans up to 500,000 rows per file, unlocks all 18 rules, exports to Excel and removes the watermark.
See Pro pricingRelated tools
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