of course there are certain patterns (im not totally familar with them) during certain times of the year. no market behaves randomly otherwise we would all be gambling trying to guess whats happens. the market responds almost completely on purpose to the economy. if something major affects the ecomony then the market will move. if that same event happens again later on traders will remember what happened and alot of their decisions will be made on historical events.many times the market responds the same way it did before. the market has a strong memory which is why its a good idea to study historical data so that when a very important level is hit, you already know what happened the last time it hit that level and you can pretty much predict what it might do again. most of the patterns or repeat behaviors usually come after imporant fundamental announcement that beat market expectation significantly or the announcements shows critical movements in the economic report(s). if you want to spend time studying periodic patterns in the market then you really should get yourself down to the fundamental section of this forum.
In life, history tends to repeat it self! The man is the only animal that bumps into the same rock twice... and if you follow and study a pattern, most likely that will be an indication of what could happen... except in the financial/trading world!!! Just keep that in mind! This could be like the lottery, you might hit big, or you might loose, but youŽll always have better odds than playing Lotto.
There are definitely patterns of price behavior in the forex market that one could call "seasonal" in nature. As has been noted already, January and December frequently see certain types of activity, as is the case in many other markets. There are some very interesting patterns in the summer months as well. If I remember the research, February through until about June, though, aren't particularly exciting when thinking in terms of position trading. There are some day to day patterns in there, though.