Preparation Day or P-Day as it is often referred to, is the one day a week in which missionaries get a break from their usual labors. It's the day that missionaries are allowed to do their laundry, shop for supplies, write letters home, and otherwise relax. The day lasts only until dinner, after which missionaries resume their normal labors. Missionaries tend to love their P-Days, as it's a nice break from the normal challenges of missionary work.