This is an Advent Calendar built in JS, with 24 doors for the days of Advent (Dec 1 - Dec 24). A door is only active on or after the specific day displayed on it. The active doors are white and clickable. After you click them an alert message with a Christmas quote pops up on the screen. The inactive doors are green and cannot be clicked.
This means that, by default, the whole Calendar is inactive before December.
In order to test the Calendar before December, comment out the month checker in the /scripts/calendar.js file, in line 24:
if( /* ( currentDate.getMonth() + 1 ) < 12 || */ currentDate.getDate() < day ) {If you want the Calendar to check for the month again just uncomment the month checker in the same line.