How can I find time to buy a train ticket?

The number under the ticket, for example, the number under a ticket is 3399-0000-1208-22-ao-60225. Where AO-60225 is the ticket number of this ticket, and the first four digits 08-22 refer to the date of purchase, but tickets sold after 16 every afternoon are displayed as the date of the next day, because the settlement of the railway ticketing system is 16.