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YYMMDD is the best date format

· One min read
Max Clayton Clowes
Max Clayton Clowes
mcclowes

I have tried every way of writing dates for files, notes, and folders. The best I have found is YYMMDD.

Why it wins​

  • Alphabetising equals chronology: 180915, 181001, 181201 will sort in the correct order in any file browser, search result, or text list.
  • Compact, fixed width: Six digits are quick to type, easy to scan, and align neatly.
  • Locale neutral: Avoids DD/MM/YY vs MM/DD/YY confusion.
  • Great for prefixes: Put the date at the start, then a hyphen, then your title. Your lists stay clean and chronological.

When to use YYYYMMDD​

If the century could be ambiguous (legal docs, historical records, or anything that might outlive you), use YYYYMMDD.

  • Example (short‑lived notes, clear context): 180915-trip-ideas.md
  • Example (long‑lived, century matters): 20180915-contract-signed.pdf

Alternatives are worse​

  • DD/MM/YY or MM-DD-YY - Ambiguous, inconsistent in standards, and they sort incorrectly.
  • MM-DD-YY is also non chronological.
  • Month names - Human-friendly, but hard to scan and sort (15 Sep 2018 vs Sep 15, 2018).

Simple rule​

Start every filename with YYMMDD-. If the century matters, upgrade to YYYYMMDD-. That is it.