CSV date format converter
Normalize dates in CSV columns to YYYY-MM-DD, DD/MM/YYYY or MM/DD/YYYY. Preserve original values and review ambiguous or invalid dates in a separate report.
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CSV date format converter
Standardize dates before importing spreadsheet exports into Excel, reporting software or databases. Choose a known day-first or month-first convention, or leave ambiguous values for review. The converter adds normalized columns and keeps the source columns. Blank, ambiguous and invalid cells remain distinct in the review report. A date already misinterpreted by another application cannot be recovered automatically.
How to use this tool
- Upload a CSV, import its direct public URL, or paste CSV text below the upload options.
- Enter exact date column names, one per line. Choose the source date convention and the output format.
- Download the CSV with new normalized columns, then review ambiguous and invalid cells before using the data.
Supported input formats
CSV
Available settings
- Numeric date order
- Output date format
Output and limitations
Normalize dates in CSV columns to YYYY-MM-DD, DD/MM/YYYY or MM/DD/YYYY. Preserve original values and review ambiguous or invalid dates in a separate report.
Comma-separated UTF-8 CSV up to 5 MB, 10,000 rows and 100 columns. Select up to 10 date columns by exact name. Four-digit years only. ISO dates are always accepted; numeric day/month dates use your selected convention. Excel serial numbers, timestamps and month names are unsupported. Formula-like cells receive a protective apostrophe.
Can I upload an Excel workbook or use Excel serial dates?
Export the worksheet as UTF-8 comma-separated CSV with dates written as text. XLSX workbooks, serial numbers, time zones and timestamps are not supported. Cell formatting alone cannot repair an incorrectly interpreted date.
What happens to an ambiguous date such as 04/05/2026?
The default review mode leaves its normalized cell blank and reports both possible dates. Choose day-first for 4 May or month-first for April 5 only when you know the source convention. The original value stays in the CSV.
What if processing fails?
Check the supported formats and file limits, then try a smaller file. Keep an original copy. A clear error message will explain an unsupported input or an unavailable processing service.