Studies of variability constitute immensely important sources of information about how objects in the cosmos form and evolve.  Variability can involve times-scales from a millisecond to a century and beyond, and it can embrace the whole electromagnetic spectrum or just one portion of it. New techniques, new technology, new data-mining skills or just more persistence are extending the realms of time-domain astronomy (TDA) and our capacity to capture information in novel and exciting ways, driving theory and inspiring searches for new kinds of phenomena.

Like its predecessor (S285) in Oxford 6 years ago, this Symposium (S339) will tackle a broad spectrum of topics by seeking commonalities among quite different kinds of objects that display similar types of variability, rather than examining in turn groups of objects that have already been classed as ‘similar’.  But while S285 presented appraisals of the many new projects then being developed, or only recently on-line, significant new surveys have since commenced and new milestones have been reached.  SKA, ALMA and SALT are also bringing southern-hemisphere astronomy into dominance in this context.  S339 therefore needs to examine critically the efficiency and scientific achievements from the new outlays of technology and equipment since 2011.  Is communication adequate?  Are follow-ups optimal?  Are data-mining tools sufficient?  Here is where the audience will supply the meeting with ideas, experiences, examples and caveats that can furnish a ‘Charter for Improvement’.