One of the points of taking notes is remembering something later. Whether you’re writing on a paper notebook, a loose sheet of paper, or on your computer, writing a title and date makes it easier for you to organize and find your note later on. Of the two, the date is the most important. You can deduce what a note is about by reading its main body, but doing so for the date isn’t easy. Because of this, it helps to write down the date every time you take a note.

If you’re capturing notes using your phone, you likely don’t have to do anything. Most note-taking apps include the note’s date as a key attribute and complete it automatically whenever you start a new note. (Many will also track other key date-related attributes, such as the date/time the note was last modified.)

But your paper-based notebook doesn’t have that feature. As a result, you must manually write the date whenever you capture a note. This doesn’t come naturally; it’s a learned behavior — and a bit of a chore. But it’s a habit worth acquiring. Writing the date on every note doesn’t take too long, and it’s helpful when you’re looking for something in the future.

I’ve built the habit of writing the date in the upper right corner of anything I write on paper. (And I also often write a title in the upper left.) I do this whether I’m writing in a notebook or a loose sheet of paper. (The exception is sticky notes, since they’re often ephemeral or meant to be clustered. When I photograph such clusters, my phone adds the date, time, and location.)

This habit has proven very valuable over the years. For example, I must sometimes look for what somebody said in a meeting months ago. Because I tag all my notes with the date, it’s easy to locate the relevant meeting minutes in my notebook. All I have to do is confirm the date the meeting happened (which is noted in my calendar) and find the right notebook on my shelves.

I can do this easily because I’ve built two habits: capturing the date on every note and writing date ranges on the completed notebook’s spine. (It’s actually easier than that, since I digitize all my paper notes. More of that in a future post.)

But paper-based notes aren’t the only ones where I capture dates: I also include the date in digital notes (and documents) that aren’t managed in an app — i.e., those I can see in my computer’s filesystem. I started doing this years ago because I realized that the computer could change the file’s creation date under certain conditions. For example, when copying a file, the computer might assign the copy date/time as the creation date of the new version.

So, whenever I write a note or create a document on my computer, I capture the date as part of its filename. While this introduces a bit of visual clutter, it makes locating the file in the system easier by sorting through file names. This practice also allows me to automate batch actions using scripts and tools such as Hazel and DEVONthink.

So, date-of-capture is an essential piece of metadata. But there’s also the question of how to write the date. There are several options available.

For example, you could spell out the month and date: November 20, 2021. If you’re tight on space or want to save time, you can shorten the month to three characters and drop the comma: Nov 20 2021. This sequence of eleven characters is unambiguous. (I don’t advise shortening the year to the last two digits, e.g., Nov 20 21 — I have flashbacks from the Y2K kerfuffle.)

Another option is to capture the date using only numbers and slashes. The month-date-year sequence varies in different countries. In the U.S., the month comes before the date, as in 11/20/2021, whereas in other countries this could be written 20/11/2021. Having only ten characters, this format is slightly more compact than the previous one. It also has the advantage that computers can sort months more easily if represented as numbers rather than names.

However, one downside is that the slash is a reserved character in many computer filesystems. Slashes are directory delimiters in Unix-based systems (such as macOS), so 11/20/2021 means “file named 2021, which is inside the folder named 20, which is inside the folder named 11” — not what you want. So, we need another delimiter.

A common one is the dash, as in 11-20-2021. This preserves the date’s legibility by visually separating the date, month, and year. It’s a significant improvement when working with computer-based files. But there’s still a downside: when listing files, computers sort based on the file name’s sequence of characters, read from left to right. In 11-20-2021, the two leftmost characters represent the month, so a set of files that start with that naming sequence would group all the November files, regardless of their year. Again, not ideal.

Instead, you want a date format that reflects your mental model: dates are contained in months which are contained in years. For the computer to properly sort file names, the year must come first, followed by the month, and then the date — as in 2021-11-20. With this format, your computer will list files in the sequence we expect when looking for a particular date.

This way of writing dates has been enshrined as an ISO standard; you’ll see it frequently in software code. It’s how I write dates, whether on the computer or paper. I’ve found it especially useful when dealing with large sets of computer files. (Note that for the file name sorting to work, the date sequence must be placed at the_beginning_ of the file name. So, a note might be called 2021-11-20 Note and not Note title

While it may be clear why this practice is helpful on the computer, you may be wondering why I also do this on my paper-based notes. The reason is simple: consistency. It pays off to settle on a standard format and use it everywhere. When I started doing this with my paper-based notes, I had no way of searching my handwriting. That has changed: I can now scan my paper notes using apps like Scanner Pro or Microsoft Lens.

Having settled on a standard date format — even if it’s one more suited to the computer’s constraints than mine — makes it possible for me to retrieve all stuff related to a particular date. If you haven’t done so already, I encourage you to start adding dates to your notes. And consider using the standard ISO date format; it makes finding things much easier once you’ve collected years’ worth of notes.