China Xian Tours list the public holiday schedules of the following 2 years to help you plan a nice Xian tour. If possible please try avoiding the Chinese holidays so your Xian tour will be more comfortable. Or if you are looking for festival atmosphere the following festival schedules will also help you choose the bet touring time.
2017 Chinese Holiday Schedule (solar calendar)
2018 Chinese Holiday Schedule (solar calendar)
Besides the public national holidays above, Chinese schools (including primary schools, high schools, senior high school, universities) have summer vacation and winter vacation. Summer vacation is basically fixed from early July to late Autumn. And the winter vacation is usually in the period from Mid January to late February depending on the Spring Festival time.
During winter vacation attractions in Xian are less crowded than in summer vacation because most people go the southern China like Sanya to enjoy warm days there.