Stellar ages: Harder than most people seem to think

The overall topic for this meeting is the evolution of circumstellar dust/gas in young stars. Nearly all of the talks address measurement or modelling of dust and gas in these environments. However, by definition, in order to empirically measure "evolution", one needs to know the ages of the stellar systems being studied. Stars do not come with birth certificates, and there is no fool-proof, quantitatively accurate observable that directly measures age. Therefore, stellar ages must be inferred from indirect indices, and those indices must be calibrated. It is important for those trying to measure the evolutionary timescales of circumstellar disks to understand the uncertainties in the ages they assign to their program stars. It is equally important that the sources of those ages be clearly documented, and that the age estimates for all stars in a sample be derived in an homogenous way. I will discuss a few topics related to age estimates for young, low mass stars and a few of the possible pitfalls.