  Variability is a defining characteristic of young stellar systems, and
optical variability has been heavily studied to select and characterize the
photospheric properties of young stars. In recent years, multi-epoch
observations sampling a wider range of wavelengths and time-scales have
revealed a wealth of time-variable phenomena at work during the star formation
process. This splinter session was convened to summarize recent progress in
providing improved coverage and understanding of time-variable processes in
young stars and circumstellar disks. We begin by summarizing results from
several multi-epoch Spitzer campaigns, which have demonstrated that many young
stellar objects evidence significant mid-IR variability. While some of these
variations can be attributed to processes in the stellar photosphere, others
appear to trace short time-scale changes in the circumstellar disk which can be
successfully modeled with axisymmetric or non-axisymmetric structures. We also
review recent studies probing variability at shorter wavelengths that provide
evidence for high frequency pulsations associated with accretion outbursts,
correlated optical/X-ray variability in Classical T Tauri stars, and magnetic
reversals in young solar analogs.
