  The measurement of an annual modulation in the event rate of direct dark
matter detection experiments is a powerful tool for dark matter discovery.
Indeed, several experiments have already claimed such a discovery in the past
decade. While most of them have later revoked their conclusions, and others
have found potentially contradictory results, one still stands today. This
paper explains the potential as well as the challenges of annual modulation
measurements, and gives an overview of past, present and future direct
detection experiments.
