SHANGHAI, Aug 31 (Reuters) - China's yuan eased on Thursday but posted its biggest monthly gain at the month-end, in percentage terms, since the Chinese currency was revalued and taken off a fixed dollar peg in 2005.
Spot yuan opened at 6.5974 per dollar and settled at 6.5969 by the 4:30 p.m (0830 GMT) domestic close. It was 3 pips weaker than the previous late session close but 0.06 percent firmer than the midpoint.
China takes the official market closing price at 4:30 p.m Shanghai time (0830 GMT) into consideration when it fixes the official guidance rate, in an effort to let market forces play a bigger role in determining the yuans value. The market also has an evening session lasting until 11:30 p.m.
If the spot rate finishes the late night session at the current level, it would have strengthened 2 percent against the greenback, the best month since July 2005.
(Reporting by Winni Zhou and John Ruwitch)