Leaving crystals on a windowsill under the full moon is meant to reset them. The windowsill is doing the same amount of work as the Moon.

Included here because it's one of the most common practices and it's worth being straight about: moonlight is reflected sunlight, roughly 400,000 times fainter, and it does not alter quartz. The honest version of the ritual is that it's a monthly cue to handle your things and think about what you're carrying.