Used to be a time when workers in offices had week numbers marked at the bottom of the page, of a desktop paper diary.
Managers and others with budget responsibilities found these particularly useful
Now folks are using smartphone calendars, Google calendars, or Lightning to help with their planning.
Marathon preparation - 12 weeks or so right?
Question: When do I need to start my running preparation if my Marathon is 1st December?
The simple answer is 48-12 = week commencing 5th September .... but some images make it clearer.
...and for folks who live in a web browser rather than at the command line ...