お勧めだったので、調べてみました。
http://www.janspiller.com/personalcharts/gpp.php

10月4日～30日の間が一番自分にとって最大のパワー発揮できる期間らしいです。
しかし、やや短い気がするな～

from October 4th (first day of your Grandaddy Power Period)

to October 30th (final day of your Grandaddy Power Period)

Please note that in some years your Grandaddy Power Period will actually begin a couple of days earlier or end a day or two later than the above dates. These calculations are set to be accurate for EVERY year, regardless of calendar changes due to leap year and other phenomena.