One of approximately five times during the forex trading day when a large amount of currency must be bought or sold to fill a commercial customer’s orders. Typically these times are associated with market volatility. The regular fixes are as follows (all times NY): 
5:00am – Frankfurt 
6:00am – London 
10:00am – WMHCO (World Market House Company) 
11:00am – WMHCO (World Market House Company) – more important 
8:20am – IMM
8:15am – ECB