Your calendar data, birthdays, names to wish, etc., are stored on your computer/tablet/phone. This method ensures better confidentiality of your personal data..
It is advisable to periodically back up this data (txt format), in order, for example, to find it again if you change computer, browser, or if you delete 'site data' in your browsing history. This backup can also be used as an export, to allow import into calagenda, on another computer, on your tablet or phone, or in another browser.