If you're looking for a no-frills tracker, Google Sheets has a free to-do list template with columns for tasks and due dates. Clicking the checkbox beside the task indicates that it is complete.

When you create a new Google Sheet, the sheet typically starts with 26 columns (labeled A through Z) and 1,000 rows (numbered 1 through 1,000). That’s 26,000 cells. You don’t have to display ...