Magic Item Attunement
Some magic items require attunement to their wearers before the bonus they grant is considered permanent. For the first 24 hours such an item is worn, the bonuses it provides are considered temporary. Temporary bonuses are sometimes excluded from certain calculated abilities and benefits.
After 24 hours, the wearer becomes attuned to the item's magic, and the bonuses it provides become permanent (affecting any derived stats), for as long as the item is worn.
Removing the magic item for brief intervals, even several days at a time, does not disrupt the magic's effects, as long as no other magic item is donned in the same slot as that item, and no other person attunes the magic item to themselves. Of course, while removed, the item grants no benefits to the (non-)wearer.
While it is attuned to a living person, the magic item grants no bonuses to a new wearer, but wearing it for twenty-four hours breaks the old attunement. Once broken, wearing it for another twenty-four hours attunes it to the new wearer. Killing the old wearer and donning the magic item breaks the old attunement immediately.
Wielded items typically do not grant attuned, permanent bonuses. Instead, they grant bonuses to their wielder only when they are actually wielded, not when carried. Exceptions to this will be called out explicitly in the magic item, or magic item property.