Honestly, I believe 25 % of the posters 10% of the time, on even numbered years with months with ending in "ary" on week days only. That is my approach. Oh ya, I also do my own research. Try it...it may work for you also.
P.S - usually the research part works out the best for me....but hey, its your money. Try either way.
Not trying to be insulting...just having a little fun.
Cheers
RustyL