If you gather the herbs at the right moment, they can unfold their power a lot better. The drying is easier and they will not mold.
The best time to gather leaves is on a waxing moon. Also quite beneficial are days in the ascending moon (Sagittarius, Capricorn, Aquarius, Pisces, Aries, Taurus), as well as leaf days (Cancer, Scorpio, Pisces).
Additionally, when gathering herbs for a specific body part, you can use the days where the moon is in the corresponding Zodiac sign. For example, you can produce a good foot cream when you gather the herbs on a Pisces day.