We are planning to visit Huashan on Jan 1, 2018. When should I buy my train tickets?

China Railway Corporation is now planning to modify the timetable and pre-sale period has been adjusted temporarily. We are planning to visit Huashan in the morning. Can I book the seat on D307 on Jan/1/2018 departing Luoyang Longmen(8:06) and arriving Huashan north(9:17) now ?