Each square is a week, month, or year from your birth date. Rich colours show completed periods; the red square is your current period; lighter colours show future periods within your chosen horizon.
Months follow calendar anniversaries and years follow birthdays. Weeks cover seven calendar days; the final week may be partial. Row lengths adjust to fit your screen, and the caption tells you how many periods each row contains.
Your horizon is editable. It does not estimate how long you will live, or how much you can do at any age.