Hi there @Rosemary7 there is a way to limit how far ahead guests can book. Once your in your calendar if you click on availability settings in the right hand corner you will see the option "how far can guests book", here you can choose the option you would like guests to arrive within three months but keep in mind that as the days are rolling the three months move ahead.
Another way you could do this would be to select the starting date you would like to block, drag the little cursor a few days along and then in the window on your right insert the correct date you would like the blocked dates to end eg. 31st December.
Hope this helps! 🙂