The database is probably the most important element, especially after you’ve invested a bunch of time adding data to it. It’s a plain text file with just three columns, separated by tabs. There’s a time stamp, then a project ID, then a description of the task. My database looks like this:

13450.36389 0 Away 13450.39059 1 Arrive, check email 13450.40014 10001 Do work on first project 13450.41707 10002 Do some different work on a second project 13450.44673 10001 Do some more work on the first project

Time stamp
The time stamp is compact because it’s a single number representing both the date and the time.
Project ID
Each project has its own unique ID, which acts as a key for more information about that project.
The description is just a sentence about the task you just completed.

Every line in the database defines one single period, but it relies on the line before it to provide the start time for that period. So all of the lines need to be in order, without gaps. The STOPTHAT software makes sure all the lines are in chronological order. It is up to you to make sure there are no gaps.