Convert Date Formats in Excel or CSV
Make every date in a column look the same.
Drop a spreadsheet here
or browse your computer
.csv, .tsv, .xlsx, .xls · Up to 10MB and 50,000 rows without an account.
By uploading you agree to our Terms and Privacy Policy. Files are deleted automatically.
Free to run and free to preview. Downloading the finished file is part of the paid product.
How it works
- 1Upload your file. We find the date columns and count how many different formats each one holds.
- 2Choose the format you want out.
- 3If a column could be read as either day/month or month/day, we ask you which it is. We will not guess — reading them the wrong way would silently move real dates.
- 4Anything we cannot read as a date keeps its original value and goes to Needs Review.
When people use this
- —An export where some rows are 09-12-26 and others are 2026-12-09
- —A file from a system that uses day/month when yours uses month/day
- —Preparing dates for an import that expects one exact format
Supported formats
This tool accepts .csv, .tsv, .xlsx, .xls. Up to 10MB and 50,000 rows without an account. We work out the encoding and the separator from the file itself, so a semicolon-separated export or one saved in a non-UTF-8 encoding opens correctly rather than as a single column of nonsense.
Questions
- How do you handle 03/04/2026?
- We look at the whole column first. A single value like 25/12/2026 settles it, because there is no 25th month. If nothing in the column settles it, we ask you — because getting it wrong changes real dates and nobody would notice.
- What formats can it read?
- ISO (2026-12-09), both numeric orders with slashes, dashes or dots, two- and four-digit years, written months in either order (9 Dec 2026, Dec 9 2026), compact 20261209, and Excel’s internal date numbers.
- What if it gets something wrong?
- It will not guess. Anything we cannot transform confidently keeps its original value and goes into a Needs Review sheet with the reason, and the workbook includes a Change Log listing every transformation and how many cells it touched. You can see exactly what happened.
- What happens to my file?
- It is uploaded over an encrypted connection, processed, and deleted automatically - within 24 hours for anonymous use. We never use anyone’s spreadsheet data to train models. You can delete a job and its files at any time from the job page.
Want the rest of the file standardized too?
The full app handles jobs that need several steps across several files, and can save the whole thing so next month takes two clicks.
Continue cleaning