A folder full of honest names can still sort in a useless order. If the date sits at the end, or the month is written as a word, the file browser sorts the alphabet, not the calendar. A date prefix fixes that with no extra software. It is a narrow rule, and it is one of the few naming rules that keeps paying you back every time you open the folder.

Write the date so the alphabet and the calendar agree

Use the year in four digits, then the month, then the day, with the parts always two digits for month and day. March is 03, not 3, because a single digit sorts in a surprising place next to 10 and 12. A file from the ninth of April in a given year then begins with that full date and lines up after March and before May. Writing the month as a name feels friendly and sorts April before January, which is not the story of the year. The broader habits in file naming that still makes sense later still matter. This rule is only about order.

Put the date at the front when time is the question

People usually open a family folder asking what happened next, not what letter the topic starts with. A prefix answers that question before anyone clicks a column header. If the important question is the topic, a topic folder can hold dated files inside it, and you still get time order within the topic. What fails is a date buried in the middle of a sentence-like name, after a word the browser treats as the start. Start with the date, then a short description: the event, the person, or the form. Stop before the name becomes a paragraph. Long names get cut off in windows and are painful to type again.

Be consistent about separators

Hyphens between year, month, and day are easy to read and do not surprise most systems. Underscores also work if you already use them. Mixing both in the same folder does not break sorting as long as the digits stay in the same positions, but it looks like two people named the files who never met. Pick one separator and mention it in the folder note. Avoid slashes. They are illegal in file names on common systems because the system thinks they are folders. Avoid a format that only one spreadsheet understands. The name should make sense in a plain file window.

Do not let the time and the topic fight

A scan of an old letter can have two dates: the day you scanned it and the day the letter was written. Choose the date a future reader will browse by, and put the other date in the note or in the description if you need it. For a letter, the written date is usually the one you will search for. For a receipt you scanned late, the purchase date is often more useful than the Tuesday you finally got to the scanner. Say which choice you made in the README so the next person does not rename the set to the other date and destroy the sort. The scanning questions in what to settle before a paper box are the right moment to decide this, before hundreds of files exist.

Prove the sort with five files before you rename five hundred

Create a test folder and drop in samples from January, February, October, and November, plus a file from a different year. If October appears before February, the month is not zero-padded or the order of the parts is wrong. Fix the pattern now. Renaming a large set later is possible and dull, and a single inconsistent file will sit in the wrong place forever because it still looks named. When the test sorts cleanly, write one example name in the folder note. People copy examples more reliably than they copy rules.

Frequently asked questions

What if I do not know the day? Use the year and month, and keep the missing day consistent, such as the first of the month, only if the note says you did that because the day was unknown. Do not invent a precise day and present it as fact.

Will this sort correctly on a phone? Most file lists sort the beginning of the name the same way a computer does. Check once on the device you actually use. If an app groups by its own date taken from inside a photo, the prefix still helps in ordinary folders.

Should every file in the house get a date prefix? Use it where time is how you will look. A program you can download again does not need one. A family letter, a scan, and a finished export usually do.

Steps

Use year-month-day: Write dates as four-digit year, two-digit month, and two-digit day.
Put the date first: Start the file name with that date so the folder sorts in time order.
Keep the rest short: Add a few plain words for the topic, using hyphens instead of spaces if you wish.
Test a sample: Drop five named files into a folder and confirm they line up from oldest to newest.