CSV date normalizer — mixed dates to ISO 8601
One column with 01/03/2024, 2024-03-01, and 'March 1, 2024' mixed together is a column that can't be sorted. We rewrite everything to YYYY-MM-DD — unambiguous, sortable, safe for every database.
Dates normalized
Before
15/03/2024 03-15-2024
After
2024-03-15 2024-03-15
Drop your CSV file here
or click to browse
The "date format" fix will be auto-detected.
What is this and why does it matter?
Mixed date formats are one of the most common data quality issues. They happen when data comes from multiple sources, manual entry mixes with automated exports, or locale settings change between users. Is 01/02/2024 January 2nd or February 1st? Without context, it's ambiguous.
CSV First Aid analyzes each column for date-like values. It detects common formats: DD/MM/YYYY, MM/DD/YYYY, YYYY-MM-DD, DD-Mon-YYYY, and more. When a column has mixed formats, the tool normalizes all values to ISO 8601 (YYYY-MM-DD), the unambiguous international standard.
Ambiguous dates (like 01/02/2024) are resolved using the column's dominant format pattern. If 90% of dates in the column use DD/MM/YYYY, the ambiguous ones are assumed to follow the same convention.
How it works
- 1Drop your CSV. The detector scans each column for date-like patterns.
- 2Mixed-format columns are flagged. The diagnosis shows how many dates need normalization.
- 3Apply → all dates become YYYY-MM-DD. Download.
FAQ
What if a date is genuinely ambiguous (like 01/02/2024)?
The tool uses the majority format in the column to disambiguate. If most dates are clearly DD/MM, ambiguous ones are parsed as DD/MM too. Edge cases are flagged as 'partial' in the fix report.
Can I choose a different output format?
Currently the output is ISO 8601 (YYYY-MM-DD). This is the safest format for data interchange since it's unambiguous and sorts correctly. Custom output formats are planned.
What about timestamps (dates with times)?
Date-time values like '2024-01-15 14:30:00' are preserved as-is. Only the date portion is normalized when the pattern is purely a date.
Related tools
CSV number format fixer
In Europe 1.234,56 means one thousand two hundred thirty-four point fifty-six. In the US it means 1,234.56. We spot the European pattern across a whole column and rewrite it to the international format — the one every database actually accepts.
CSV whitespace trimmer
A single trailing space is why your VLOOKUP misses, why two rows look like duplicates but aren't, why the join silently loses half the records. One pass trims every cell — matches start working again.
Fix CSV encoding
Seeing é, ü, ö where you expected é, ü, ö? The file was saved in one encoding and read in another. We figure out which one, then convert to UTF-8 so Müller looks like Müller again.