At the start of each year, the Treasury publishes a calendar in the Boletín Oficial del Estado setting out the auction dates for Government Debt instrument, with dates for the presentation of bids and the settlement and issue of securities.
The calendar published may be modified as the year goes on, depending on the needs and opportunities arising for the Treasury or the market itself. Special auctions may be called, for instance, for the launch of new Public Debt instruments. Also, the Treasury can cancel a scheduled auction included in the calendar.