Some teachers choose a different teaching theme every week, every two week or monthly. Preschool monthly themes can be based on holiday, celebration or season in every month.
Some holiday and festival is an international celebration that will be same for every country and region such as Valentines Day on February, 14th; Christmas on December 25th or Chinese New Year.
But some holiday is depend on each region and country, for example : in USA and Canada - Father Day is celebrated on third Sunday in June, while Australia and New Zealand - Father Day is celebrated on first Sunday in September and some country do not celebrate Father Day at all.
Teacher should adapt the monthly preschool themes to fit to their class need.