Answer
One event that could shift the demand curve for labor is a change in the price of a good. If the price of a good increases, then the value of the marginal product of each worker also increases. If the price of a good decreases, then the value of the marginal product of each worker also decreases.
Work Step by Step
Another event that could shift the demand curve for labor is technological change. If there is a technological advance, then the marginal product of labor also increases. This, in turn, increases the demand for labor.