Two filenames. `Invoice_Acme_2025-08-15.pdf` vs `2025-08-15_Acme_Invoice.pdf`. Same information. Different consequences.
The second one sorts chronologically. The first one doesn't. Across a folder of 200 PDFs, the difference is enormous.
Alphabetical sorting becomes chronological
When the date is at the start of the filename in `YYYY-MM-DD` format, alphabetical sorting gives you chronological order. The list reads like a timeline. Most recent at the bottom (or top, depending on sort direction).
When the date is at the end, alphabetical sorting is by counterparty or doc type, which is also useful but doesn't tell you when. Dates-first wins for chronological browsing.
Search becomes precise
Need August 2025 documents? Type `2025-08` in the file search. Every relevant PDF surfaces. Same trick for 'all Q3 2024' (`2024-09`, `2024-08`, `2024-07`).
With dates elsewhere in the filename, the search has to be smarter and often misses. Dates first puts the date in the indexed prefix position.
Year-on-year comparisons get easy
Two folders, one for each year. Identical naming convention. Spot-checking 'where were we this time last year' is a folder switch and a glance, not a database query.
This matters more than people expect. Patterns reveal themselves when the data is organised by time.
The cost is five seconds
Per file, you spend five seconds typing the date prefix. Multiply by 10 PDFs a day, that's 50 seconds. Over a year, 200 minutes of typing.
In return, you save 30 seconds per file search (and you search dozens of files a week). The maths is overwhelmingly in favour of dates-first.
FAQ
What if the document doesn't have a clear date?
Use the date you received it or the date you created it. Approximate is fine; the structure matters more than precision.
What format should the date be?
`YYYY-MM-DD`. ISO 8601. Sorts alphabetically as chronologically. Avoid `DD-MM-YYYY` (doesn't sort) and `Aug-15-2025` (doesn't sort, language-dependent).
Should I include time in the filename?
Rarely. For high-frequency timestamps (logs, scans), include time. For most professional documents, the date is enough.
What if I have old files without dates in the filename?
Rename as you touch them. Don't try to fix the entire history; fix the present and prevent the future.
Five seconds per file, forever. The smallest naming change with the biggest payoff. Rename your next PDF in Flint and feel the structure click.