Estimating accurate stellar ages is one of the most difficult challenges in astrophysics. A star's age cannot be measured directly, and currently we only know the accurate age for one star: the Sun. Stellar ages lie at the heart of much of astrophysics. The accurate determination of timescales for physical processes in the stars allows us to compare the properties of stars at different stages in their lives. In IAU Symposium 258 astrophysicists from around the world discuss the current state of the problem of estimating ages of stars and stellar populations. They describe their efforts to better constrain the ages of individual stars and groups of stars through improved observations and physical models. IAU S258 highlights where the advances are being made and predicts what the near future offers.
