In brief: I have two shortcuts for this: “Now” and “Stop”.
“Now” accepts text input or prompts for a title, then creates an event in my calendar with “#runningtimer” attached. It also offers a few default event durations (20m for a pomodoro, 1hr, 2hrs…) and sets an alert for the end of the event. This is important for me because I always forget to stop a running timer!
“Stop” accepts text input (to match event title) or prompts to select from any events in the past day that have “#runningtimer” in their title. To be tidy, the shortcut removes the text tag from the selected title, and edits the end time to match the time at which the shortcut was run (deals with running over or under anticipated time). “Stop” also tests for the presence of a few other possible text tags in the title (e.g. “#reading”) and, if any are present, logs the time to an appropriate Nomie tracker.
If a time-tracked session is related to a project, I’ll include a project code in the event title. That way I can easily visualise time spent on any project in Timeview, or run another shortcut to list all records related to a specific project in Drafts (and so produce a basic timesheet, although the work I do doesn’t formally require that kind of reporting). Of course, the same is true for any specific activity I might want to tally/analyse time for— all I need is a sensible identifier for whatever I want to pay attention to.