In the financial field, "T day" and "T + 1 day" usually refer to the trading and settlement time of financial products such as stocks and funds.

T day (trading day) refers to the day when financial products (such as stocks, funds, futures, etc.) can be bought and sold. On T day, investors can submit buy or sell orders and participate in market transactions. It should be noted that transactions on T day need to be conducted within the trading time range of that day, and different markets may have different trading hours.

T+1 day (the first working day after the transaction day) refers to the day when financial products are settled on the next working day after completing the transaction on T day. On the T+1 day, both parties to the transaction need to clear and settle the transaction, including payment of price, transfer of securities, etc. Therefore, financial products purchased on T day usually need to be sold on T+1 day.

It should be noted that different markets and financial products may have different trading and settlement rules. In some markets, settlement may take place on T+2 or longer. When conducting financial transactions, you need to understand the specific rules of the relevant market to ensure that the transaction proceeds smoothly.