Note Numbering System

Make your notes sortable, searchable, and linkable, even if you take notes on paper or use an app that doesn’t natively support linking. See my Note Numbering Tool for a quick way to copy/paste these numbers into your own electronic notes.

This is the number system I use for my my own notes and an explination of my rationalle for parts of it. If you find it useful, feel free to adopt this number system or adapt it to your own.

I’m going to delve into details here but the number system is very simple. You just use the current time. But, let me tell you about exactly how I format those numbers and why I chose this system.

The Format

YYMMDDHHMM

This results in a 10-digit number. Here’s a longer explanation of that format.

I also add a small prefix to the beginning of this number, which I’ll get to shortly.

Two Digit Year

As a software engineer I typically prefer a four digit year. But, I use a two digit year for my numbering system.

I won’t take personal notes for more than 100 years, so my note numbers will never roll over. Two digit years should be okay for most of us, even if we stuck to this our entire lives. This really just saves two characters so we end up with nice round 10-digit numbers.

The NN Prefix

When refering to a note, in the body of another note, I refer to it with a prefix. I add the litteral string “NN” to the front of the number, which stands for “Note Number”. Here’s an example note number.

By putting a prefix on the number you can do interesting searches. For example, a search for “NN24” lists all notes from 2024. “NN2404” lists all notes from April 2024. That’s pretty useful.

You can use these prefixed numbers to search for a note on a subject you remember writing and then search for other notes you wrote close to that date by their partial note number. For example, I might search for “universe” and see notes numbered 240304xxxx and 203006xxxx. Then I can search for notes labeled NN240304 and NN240306 to see what other notes I wrote on those same days, which could give me notes that I wrote at the same time but where I might not have mentioned the original search phrase.

I currently use Google Keep as a primary place to store notes. On iPhone, Google Keep treats 10-digit numbers as phone numbers and updates the links to that. Putting a prefix on the number prevents that.

Another advantage of a prefix is that if you use a lot of numbers in your notes you could have collissions with those numbers. Adding a prefix should prevent that.

Time Zone

I use the current time zone when I write a note. The main reason is for daytime context. If I write about a sunset, I want the note number to capture the time from my own perspective at the time.

A downside to using the current time zone is that it creates some possibility of collissions.

Note Number Collissions

There are times that you could run into duplicate note numbers (collissions). This can happen for a couple reasons.

One place you can run into duplicates is during time zone changes. That happens for switches from daylight to standard and back as well as when you travel. In those cases you’ll have an overlap of whatever that time change is. For most of us, that will be relatively rare. If you’re an executive who travels a lot, however, you might want to alter this system to account for your travel.

My solution is not to worry too much about these. If I notice a collission, I’ll manually time shift my note number by a minute. A minute one way or another won’t be a big deal for me. Duplicate note numbers aren’t a very big deal for searches either. They could be a problem with filenames. I deal with collisions if and when they come up.

If you do need to account for differences in time zone, here are some suggestions.

Filenames

When I store notes as electronic files, I use the note numbers as filenames. Using the example from above, a note might be saved as 2403150545.txt. This allows you to list files in a directory in chronological order (newest to oldest or oldest to newest).