This paper investigates the differential predictive power of overnight and intraday returns in China's A-share market. We find that overnight returns exhibit a significantly positive and robust relation with future stock returns at intermediate horizons, whereas intraday returns display no comparable predictive effect. Mechanism analysis indicates that this predictability is primarily driven by the T+1 trading rule, which restricts timely selling and leads to an underreaction to negative information. Further analyses show that overnight returns embed information about future earnings, suggesting that they capture the delayed incorporation of fundamental news resulting from institutional trading frictions. Our findings differ from patterns documented in developed markets and offer new insights into the price discovery process in emerging equity markets.