12 refers to the year of the contract, 20 12, the last two digits indicate the expiration month, and the due delivery date is the third Friday of the expiration month. In case of holidays, it depends on the trading tips of the relevant exchange.

As for stock index futures, there is generally no signing date. In fact, it is a formatted contract form. Generally speaking, the buyer and the seller are established by one buyer selling (shorting) the contract and another buyer buying (shorting) the contract, which leads to their opposite positions.