British Pound (IMM): (High: Nov-Jan//Low: Feb-Mar or Sep) UK fiscal year begins Apr 1. Currency has tended to be weakest at end of fiscal year (Feb-Mar) and at mid-point (Sep), strongest in first month of each calendar quarter.
Against the USD, the Pound has two months in which it has shown a notable directional tendency. They are September and December, as can be seen below. In the case of the former, GBP/USD has risen six of the last seven years, averaging an increase of over 230 pips for the month in that span. Actually, 2005 broke a string of twelve consecutive September gains in the pair.