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klog is a plain-text file format and a command line tool for time tracking. It is free and open-source software distributed under the MIT License.

Find the source code on Github:

Get klog

  1. Download the latest version and unzip
  2. Right-click on the binary and select “Open” (due to Gatekeeper)
  3. Copy to path, e.g. mv klog /usr/local/bin/klog (might require sudo)
  1. Download the latest version and unzip
  2. Copy to path, e.g. mv klog /usr/local/bin/klog (might require sudo)
  1. Download the latest version and unzip
  2. Copy to path, e.g. to C:\Windows\System32 (might require admin privileges)

As an alternative you can also use the Linux binary on the Windows Subsystem for Linux.

In order to not miss any updates you can either subscribe to the release notifications on Github (at the top right: “Watch” → “Custom” → “Releases”), or you occasionally check by running klog version.


The idea behind klog is to store data in plain-text files in a simple and human-readable format. The notation is similar to how you would write down the information into a physical notebook using pen and paper. Manipulating your data is as easy as opening the file in a text editor and making changes to the text. By using the klog command line tool you can search, evaluate and manipulate your data from the terminal.

Screen recording of the demo described below

Let’s say you started a new job and want to use klog for tracking work times:

First day at my new job
8:30 - 17:00
-45m Lunch break

At the 24th of March 2018 you came to the office at 8:30 in the morning and went home at 17:00 in the afternoon. Somewhere in between there was a 45-minute lunch break.

As you see, klog supports different notations to record times. You can capture short summaries about your activities along with the time data (only if you want, of course), which can help you later on to make sense of what you did back in the day. And by adding tags you are able to run more fine-granular evaluations.

When stored in a file (e.g. worktimes.klg) you can use the klog command line tool to interact with it. For instance, you could evaluate the resulting total time like this:

klog total worktimes.klg
Total: 7h45m
(In 1 record)

In case you want to add an extra 30 minutes, you can do:

klog track '30m' worktimes.klg

File Format

Version 1.0

klog is based on plain text files that hold the data. The file extension is .klg.

A .klg file can contain any number of records that each consists of a date, time entries, and (optionally) summary texts.

First day at my new job
8:30 - 17:00
-45m Lunch break

8h15m Onboarding and introduction

Started to work on a first small
project (new sales brochure)
8:50 - 12:45
14:00 - 16:00
16:20 - 18:00

Records are separated by one blank line between them. The first line of a record must be a date (formatted either YYYY-MM-DD or YYYY/MM/DD).

An optional block of summary text may follow underneath the date. The time entries appear afterwards and are indented by one level.

Time entries

Entries are the actual time values that you track. Each entry represents an amount of time that you spent on something. The computed total time of a record is the sum of all its entries. Entries appear one per line and are indented by one level. They start with the time value and can be optionally followed by a summary text.

8:00 - 9:00

Both entries in this example are worth 1 hour each, resulting in a total time of 2 hours for this day.

Entries can be:

The indentation is either 1 tab or 2–4 spaces. The order of entries can be arbitrary and has no influence on the result. There can be any number of entries per record.


The purpose of summaries is to capture arbitrary information alongside the data for future reference.

Woke up this morning with the plan
to make the world a better place
10h Watched movies

Summaries are optional and can appear:

Tagging / categorising

Summaries can contain #hashtags that allow for more fine-granular filtering of the data later on.

Did some #sports
2h #badminton session with Max
1h Went out for a #run

If a tag appears in the overall record summary, then all entries will match when filtering for that tag. If a tag appears in an entry summary, only the respective entry will match.

In this example, the total time for the tag #sports would be 3h, and the total time for #run would be 1h.

Tip: The klog CLI supports wildcard searching at the end of tags, so e.g. --tag=sports... would match the tag #sports_run. That way you can structure your tags in a hierarchical way.

Open-ended time ranges

In case you just begin an activity (without knowing when it will end) you can already log it in your file as an open-ended time range.

Started to read my new book
16:30 - ?

Open-ended time ranges are denoted by replacing the end time with a question mark, otherwise they work the same as normal entries. Note, that there can only be one open-ended range per record, and it doesn’t count towards the total time as long as it’s open.


For some use-cases it’s helpful to specify a certain overall time goal that you want to achieve. This is called “should-total” in klog. It is a duration value, followed by an exclamation mark and wrapped in parenthesis, which appears after the date of the record. For example, let’s say you are supposed to work 7½ hours per day:

2019-07-26 (7h30m!)
8:00 - 16:00 Work
-45m Lunch break

When evaluating the record you can calculate the difference between should-total and actual total time, in order to see whether you have reached your designated goal. A should-total value always applies to the entire record with all its entries.

Day shifting

Sometimes you start an activity in the evening and end it after midnight, just so that start and end time don’t belong to the same calendar date. For this case it is possible to “shift over” a time to the previous or to the next day by adding the < prefix, or the > suffix respectively.

<23:30 - 8:00 Worked a night shift
22:30 - 1:45> Watched some movies

When filtering records, keep in mind that these entries are still associated with the date they are recorded under, so the total time for the above date 2019-07-26 is 11h45m. (If there are records for the adjacent days, their total time won’t be affected.)


Is it possible to use to-the-second precision, like 1h10m30s or 8:23:49?

No, this is not supported. The reason is that it would effectively prohibit mixing values with and without seconds, which leads to a lot of hassle. Keep in mind, klog is for tracking time of activities, it’s not a stopwatch.

Can I capture timezone information?

No. In case you are affected by a timezone change or a switch to daylight saving time you need to account for that yourself. Realistically, this doesn’t happen all too often anyway, so it’s a tradeoff for simplicity to omit the timezone information altogether.

Can there be multiple records for the same date in one file?

Yes, as many as you want.

Can a record be empty?

Yes. The only requirement for a record is that it contains a date. Apart from that, it can be empty.

Do records have to be sorted in a specific order?

No, the order is up to you.

How many entries can a record have?

As many as you want, including none and five thousand. You can also freely mix the different kinds of entries (durations, negative durations, time ranges). The only exception are open-ended ranges, of which there can only be one per record.

Are there any logical constraints when tracking times?

klog generally doesn’t impose too many restrictions. Examples of things that are allowed: tracking more than 24h per day; tracking only negative durations; time ranges that overlap; negative should-total values.
There might be valid reasons for such use cases, so klog deliberately is not stricter than necessary.
What the command line tool does do, however, is to raise warnings about certain potential issues, for example when it detects an open-ended time range at a past date.

Are summaries mandatory?

No, summaries are optional. They are a way to keep notes that help you keep track of what you did.

Can I organise records throughout multiple files?

Yes. klog is not opinionated about the way you structure your data across files and folders. It’s actually useful practice to have separate files, e.g. one for each month or for different kinds of activities. When you evaluate files using the CLI tool, you can always pass multiple file names, or you can make use of glob patterns (e.g. 2021-*.klg, which expands to 2021-01, 2021-02 etc.). This, along with tags, allows you to come up with a structure that meets your personal needs.


You find the formal specification of the file format in the repository.

Command line tool


The command line tool allows you to find and filter records in files, pretty print and evaluate them, and apply some basic manipulations. The following sections demonstrate the usage of the subcommands. (They are not a complete reference, though.) In order to learn about all flags and options please run klog with the --help flag (which is also available on the subcommands).

In case there are syntax errors in the input text, klog cannot process it and displays an error message instead, which hopefully helps you fix the problem. Also some commands emit warnings to draw your attention to potential logical issues in your data.

For the evaluation commands you can specify input in one of the following ways:

Pro-tip: most shells have native support for glob patterns, so in case you want to organise your records throughout multiple files (e.g. one file per month) you can process them all at once by passing the glob pattern *.klg.


With the print subcommand you can pretty-print one or multiple files onto the terminal. You can apply filters in case you look for something specific. Printing is a good way to double-check that the syntax in a file is all correct.

klog print worktimes.klg
First day at my new job
8:30 - 17:00
-45m Lunch break


The total subcommand evaluates the total time of the records from one or more files.

klog total sport.klg
Total: 60h36m
(In 15 records)

If you want to evaluate all records in sport.klg since January 2018 that are tagged with #workout, you would do:

klog total --since=2018-01-01 --tag=workout sport.klg
Total: 20h21m
(In 7 records)

Remember that open time ranges are not taken into account by default. You can factor them in by passing the --now flag.

In case you set should-totals for your records you can use the --diff option to calculate the difference between the should-total and the actual total:

klog total --diff sport.klg
Total: 16h45m
Should: 18h!
Diff: -1h15m
(In 6 records)


Prints a report of the records as a timeline (like in a calendar), listing all days and their total times.

klog report 2020.klg
2020 Jan Wed 28. 6h20m
Sun 30. 3h50m
Feb Tue 3. 7h
Fri 5. 6h15m

Use with the --fill option to print a consecutive stream of all dates.


Displays an overview of all available tags and a breakdown of the aggregated total times for each of them.

klog tags sports.klg
#running 13h
#biking 9h
#sports 21h


Evaluates the total time, where today and all other records are displayed separately. (In case there are no records today, it falls back to yesterday.)

klog today times.klg
Today 5h7m
Other 162h19m
All 167h26m

By using the --follow flag you can keep the shell process open and see your data being updated live.

In case you have set should-total times, then --diff and --now will forecast the end-time at which your designated time goal will be reached.

klog today --diff --now times.klg
Total Should Diff End-Time
Today 5h7m 8h! -2h53m 18:00
Other 162h19m 160h! +2h19m
All 167h26m 168h! -34m 17:26


Add a new entry to a record:

klog track '1h30m' sports.klg

The entry will be added if there is already a record at that date. Otherwise a new record will be created and inserted into the file.

If you don’t specify a date then klog will look for a record at today’s date. Say, today was the 14th of February 2012, then the above example command would append a new entry so that the resulting record would look like this:

8:15 - 9:45 Morning run

You can not just track time values that way, but you can also add the summary text right away. (Effectively, the argument is just the entire entry line as it is supposed to appear in the record.)

klog track '8:00-16:00 Workday' work.klg

Note that you should wrap the value into single quotes in order for your shell to treat it as single argument and to avoid special characters to be interpreted. In case you want to track a negative duration please remember to escape the leading minus with two backslashes:

klog track '\\-30m Coffee break' work.klg


Starts a new open-ended time range:

klog start work.klg

The open-ended range will be added as a new entry if there is already a record at that date. Otherwise a new record will be created and inserted into the file. You can also specify a date explicitly through the --date flag.

By default the current time is used as start time. You can optionally specify it with the --time 5:00 flag. If you want, you can use the alias klog in.


Stops an ongoing open-ended time range:

klog stop work.klg

It works in the same way as klog start does. If there is no open-ended range at the specified date it will look for on at the previous date and close that with a shifted time.


Creates a new record:

klog create reading.klg

By default the current day is used as date. You can also specify a date explicitly via the --date flag. The command assumes the records in the file to be in chronological order and inserts it at the right position. You can specify a should-total via the --should flag.


Configure a default file for klog to read from:

klog bookmark set my-current-file.klg

When a bookmark is set, you don’t have to specify an input file for the subcommands anymore. (You are still able to, though.) Bookmarking is a useful convenience so that you don’t have to browse to a specific working directory all the time. Instead, you can interact with your bookmark from any location:

klog total --today

You can also quickly open up the bookmark in your favourite editor (based on the $EDITOR environment variable).

klog bookmark edit


Converts records into a JSON data structure that allows you to process the data by means of other tools or scripts programmatically.

klog json somefile.klg

The output structure is not explicitly documented yet. Run it with the --pretty flag in order to explore the output structure, it should be largely self-explanatory.

Remember that klog checks stdin for input as well, which might be handy when you invoke it as subprocess from another program.

widget (MacOS only)

On MacOS there is an experimental menu bar (systray) widget bundled into the command line tool. It displays an ongoing counter of the current day and the statistics of a file. As source file the bookmark is being used. You can launch the widget by running:

klog widget

Use the --detach option to run the widget standalone (detached from the shell process).


Displays which version of the command line tool you are on. This also checks online whether there is a new version available.

klog version


This is an ongoing collection of all kinds of extensions around klog. If you have built a utility for klog, please open an issue so that it can be added to this list.
In case you need the klog logo for anything, see here.


Editor plugin for VSCode for syntax-highlighting and snippets.
(Maintained by @vladdeSV)