One of the very best day to harvest wood that has the best properties for making musical instruments, according to the moon-calender and the old, almost lost knowledge our ancestors had about such things, was Nov. 15th in 2017. Fortunately everybody involved was free. In recent decades, some research has been done on so-called moon-wood, and it showed there was more to these old traditions than everybody had expected! A well known study, e.g. is that from Ernst Zürcher, linked here in English and Deutsch.