Refer to Get forex. Forex rates change at least three times on a Malaysian Banking business day at 11am, 3pm and 7pm (GMT+8).
Rates will be reflected half an hour earlier (You may get your incoming rate at 10.30am, 2.30pm, 6.30pm) before they take effect. Use the API method Get_ForextNextRate.
Example:
Friday 7pm rate will be used until Monday 10:59am
Tuesday 11am rate will be used until Tuesday 2:59pm
Thursday 3pm rate will be used until Friday 6:59pm