The announcement comes via the PBOC and will go into effect from 3 January. This will see the domestic interbank FX market, the ChinaForeign Exchange Trade System (CFETS), observe trading hours until 3.00am local time (from 11.30pm currently).
The time for the fixing for the yuan currency and spot closing both remains unchanged though at 9.15am and 4.30pm local time respectively. The change to the trading hours above is said to "promote the development of the foreign exchange market and expand high-level opening". The full announcement can be found here.