How to use:

December 1st, 2024 is set as your start date (highlighted with a blue ring)
Click on dates to mark individual days spent in the country (will be filled in blue)
Use Shift+Click to select a range of dates: first click sets the start (green ring), second click fills all days up to that point
The calculator will check if you maintain at least 90 days of stay in every 180-day period, starting from May 29th, 2025 (180 days after start)
If you don't have enough days in any period, it will show when this happens (date highlighted in red) and how many days you're missing
Click a marked date again to unmark it
Your marked days are automatically saved and will persist even if you close the browser
Use the "Clear All Days" button to reset all marked days