No complex apps; you just need to know the idea

One Page Notebook Update

Before getting into more calendar geekiness, a comment on the One Page Notebook, which I’m still using daily. Making the first fold parallel (rather than perpendicular) to the long edge gives you two double page spreads before needing to refold the page to reveal more writing space.

The calendar.txt concept

Calendar.txt1 is a completely manual way to plan your time and keep track of events. It makes an ideal companion to the todo.txt task management system. According to the calendar.txt documentation, “To use calendar.txt, you just need to know the idea.”

Calendar.txt rules

So here’s the idea:

1. Get yourself a list of dates2
2. Write what you plan to do next to each date

And here are the rules:

• One thing per line
• Use ISO 8601 date format3 (YYYY-MM-DD, e.g. 2025-09-29)
• Week starts Monday
• Leave 2 spaces between the date and events, and between events
• Times use the 24-hour clock
• Write times in the timezone local to the event

Optional:

• Use +tags for repeating events, projects
• Use @contexts for tasks related to specific people, places, or things

I love this kind of simplicity! It’s the digital equivalent of paper and pen, with the convenience of search and edit.

Testing it out

This week (and next) I’m away from home, spending time with family. The perfect opportunity to test out calendar.txt! It’s like the different perspective of life you get from putting on a new set of clothes, or reorganising the furniture.

Obsidian works with Markdown files, so my calendar file is currently named calendar-txt.md. A shortcut to this file sits on my iPhone home screen for speedy access. I highlight each day the night before ==like this==, so it a) stands out in the list, and b) is quick to find. It’s a lot faster to search for == than it is to enter today’s date or to scroll to the right spot.

You can use calendar.txt in the command line and grep your way to quickly displaying the information you need to see. I haven’t yet mastered those skills but I’m getting by very nicely in Obsidian, and in VS Code when I want more selecting and editing power. Vim mode in Obsidian will be another option when I’m ready for it.

During this testing phase I’m keeping things very simple indeed. No Markdown sections for easy outline navigation, though I may give into that temptation in the future.

To view all instances of an event in a sidebar list in Obsidian, let’s say everything tagged +french, I enter file:calendar-txt line:+french into the search box. Strings of text require quotation marks: `file:calendar-txt line:“Bins (R, Y)”.

A future planning tool with a safety net

I love Calendar.txt for its future-proof simplicity. Weeks of the year are an integral part of it, which I appreciate. I can access my calendar on desktop or mobile devices, and I can work with it in any text editor. And a truly huge advantage: it has version control, something you won’t find in a regular calendar app.

Not directly related, but Beorg, my main task manager, can automatically generate a text file of calendar items directly from Apple Calendar. It’s a backup in human readable plain text format that sets my paranoid heart at ease. And should I one day conquer Mount Org (deeply nestled in the Valley of Emacs) it will be useful there, too.

Calendar.txt will likely be a planning scratchpad going forward rather than my core calendar. It’s another time travel portal that can help the future feel like somewhere I have already been.

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Calendar.txt was created by Tero Karvinen, and is not officially associated with Gina Trapani’s todo.txt. I discovered calendar.txt via Ploum’s blog post.↩︎ 1.

Dates up to 2033 can be downloaded from calendar.txt↩︎ 1.

Because why would you use anything else?↩︎

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