About

Files named with inconsistent date formats - March 15, 2024, 15-03-2024, 03.15.2024 - create sorting chaos. Alphabetical ordering breaks. Search fails. Backups become unreliable. This tool parses over 15 common date patterns from filenames and normalizes them to ISO 8601 format (YYYY-MM-DD), which sorts lexicographically and chronologically. It runs entirely in your browser. No files are uploaded to any server.

The parser handles written months (January through December), numeric formats with various delimiters (hyphens, dots, slashes, spaces), ordinal suffixes (1st, 2nd, 3rd), and ambiguous day/month resolution configurable by the user. Files that contain no recognizable date pattern are flagged but preserved. Limitation: the tool assumes dates refer to the Gregorian calendar and does not validate against impossible dates like February 30.

Formulas

The renaming algorithm applies a priority-ordered chain of regular expressions. Each pattern attempts to extract three date components: year (Y), month (M), and day (D). The output filename follows this structure:

output = Y − pad(M, 2) − pad(D, 2) + " " + remainder + ext

Where pad(n, 2) zero-pads to 2 digits, remainder is the filename with the date substring removed and whitespace/delimiters cleaned, and ext is the file extension preserved verbatim.

For two-digit years, a pivot rule applies:

{

Y = 2000 + yy if yy < 70Y = 1900 + yy if yy ≥ 70

Month name resolution uses a lookup table mapping both full names (January → 1) and three-letter abbreviations (Jan → 1). The match is case-insensitive. Ambiguous numeric dates (e.g., 03-04-2024) are resolved by the user-selected locale preference: MM/DD (US) or DD/MM (EU).

Reference Data

Input Pattern	Example Filename	Renamed Output	Regex Strategy
Month DD, YYYY	Meeting Notes March 15, 2024.md	2024-03-15 Meeting Notes.md	Full month name + day + 4-digit year
Mon DD, YYYY	Report Jan 5, 2023.docx	2023-01-05 Report.docx	Abbreviated month + day + year
MM-DD-YYYY	invoice 03-15-2024.pdf	2024-03-15 invoice.pdf	Numeric with hyphen delimiter
DD-MM-YYYY	notes 15-03-2024.txt	2024-03-15 notes.txt	EU format (user config)
YYYY-MM-DD	2024-03-15 already correct.md	2024-03-15 already correct.md	ISO 8601 passthrough
MM/DD/YYYY	scan 03/15/2024.png	2024-03-15 scan.png	Slash delimiter US format
DD.MM.YYYY	foto 15.03.2024.jpg	2024-03-15 foto.jpg	Dot delimiter EU format
Month DDth, YYYY	Birthday March 15th, 2024.md	2024-03-15 Birthday.md	Ordinal suffix stripped
DD Month YYYY	15 March 2024 report.md	2024-03-15 report.md	Day-first with written month
YYYYMMDD	backup_20240315.sql	2024-03-15 backup.sql	Compact 8-digit date
MM-DD-YY	log 03-15-24.txt	2024-03-15 log.txt	2-digit year (pivot at 70)
Month YYYY	Budget March 2024.xlsx	2024-03-01 Budget.xlsx	Month + year only, day defaults to 01
YYYY_MM_DD	data_2024_03_15.csv	2024-03-15 data.csv	Underscore delimiter
DDth Mon YYYY	15th Mar 2024 memo.doc	2024-03-15 memo.doc	Ordinal + abbreviated month
No date found	random_notes.md	SKIPPED	No pattern matched

Frequently Asked Questions

You select your preferred locale (US: MM/DD or EU: DD/MM) in the settings panel. The tool applies that interpretation consistently to all numeric-only date patterns. When a written month name is present (e.g., 'March 4'), no ambiguity exists and the locale setting is ignored for that file.

They appear in the preview list flagged as "No date found" with a distinct visual indicator. They are excluded from the download batch by default. You can toggle an option to include them unchanged in the output ZIP.

No. The tool creates renamed copies packaged into a ZIP file that you download. Your original files remain untouched. The browser's File API provides read-only access to the selected files.

A pivot year of 70 is used. Values 00-69 map to 2000-2069. Values 70-99 map to 1970-1999. This follows the same convention used by POSIX and most spreadsheet software.

The parser uses the first match from the highest-priority pattern. Priority order: ISO 8601 (YYYY-MM-DD) first, then written month names, then numeric formats. If the wrong date is selected, you can manually edit the output name in the preview table before downloading.

Yes. The parser validates that the extracted month is between 01-12 and day is between 01-31. Numbers like 20241345 would fail validation and be skipped. However, a number like 20240115 that happens to not be a date will still match. Review the preview before downloading.