Standardize dates in a CSV

Automatically detect multiple date formats in a CSV column (DD/MM/YYYY, YYYY-MM-DD, “15 March 2024”…) and convert them to a single target format.

Example:
Drag and drop a .csv here, or paste its content below. 25 MB max.

How it works

An export from multiple sources often contains dates in different formats (DD/MM/YYYY on one side, YYYY-MM-DD on the other, sometimes even written out in words): this mix makes sorting and calculations impossible. Enter the column concerned and the target format; the tool automatically recognizes the format of each cell and rewrites it consistently.

How does the tool resolve the ambiguity between DD/MM and MM/DD?

For a numeric format like “03/01/2024”, if the first number is greater than 12, it is necessarily interpreted as a day (so DD/MM/YYYY); otherwise, the tool assumes DD/MM/YYYY by default, the most common day-first format. If in doubt about your data, check a few rows in the preview before downloading the result.

What happens if a value is not recognized as a date?

The cell is left unchanged in the result, and a message tells you the number of unrecognized values so you can correct them manually if necessary.

100% local processing: date detection and conversion are done entirely in your browser; your CSV file is never sent to a server.