Date Format Fixer
Batch-fix CSV date columns — detect ambiguity, set region preference, export ISO/US/UK.
Preview will appear here
Fix ambiguous dates and broken CSV imports
Date Format Fixer is FormatList's full-workflow tool for messy date columns. Paste hundreds of rows, upload a CSV export, or fix dates after Excel corrupted your import.
What this tool does (that others don't)
- Batch processing with row-by-row stats
- Ambiguity highlighting — never silently guess 03/04/2025
- Preference control (US / UK/EU) for mixed-source data
- Output in ISO, US, or UK format + CSV download
- Excel serial numbers (e.g. 44927)
Workflow
- Paste or upload your date column
- Review ambiguous rows (amber highlight)
- Set Preference if you know the source region
- Choose Output format → Copy or Download CSV
- Continue with CSV to JSON for API integration
Not sure if one date is ambiguous? Try the Ambiguous Date Checker. Converting UK forms to US? Use UK Date to US Date.
FAQ
Is 03/04/2025 March 4 or April 3?
It depends on the source region. This tool flags it as ambiguous and shows both readings. Set Preference to US or UK/EU once you know where the data came from.
Why does Excel change my CSV dates?
Excel applies your computer's regional settings when opening CSV files. Import via Data → From Text/CSV and mark date columns as Text to preserve original values.
Can I fix multiple dates at once?
Yes — this is the batch tool. Paste one date per line or upload a CSV. For checking a single ambiguous date, use the Ambiguous Date Checker instead.
What is the safest date format for CSV exports?
ISO 8601 (YYYY-MM-DD) is unambiguous internationally and sorts correctly as text.
Is my data sent to a server?
No. All parsing runs locally in your browser.
Related converter tools
Fix dates, then continue your data workflow with these browser-based converters.