Last minute train ticket availability for Beijing - Xian-Zhengzhou-Beijing

Generally, impossible to get a train ticket to Xian from Beijing on the same day or a day earlier. If you are lucky to get one, it is a seat ticket. We usually book it at lest 5 days before departure. There are many bullet trains from Xian to Zhengzhou and Zhengzhou to Beijing, train ticket is available on the same day or a day earlier. So, you just need to buy ticket earlier for the first trip. When you just get to the next stop, buy ticket right at the airport for the following trip. I mean when you arrive Xian Railway Station, just buy the ticker ready for Xian-Zhengzhou.