Phenology is one of the most basic traits affecting organisms and ecosystems. Nearly all ecological relationships and processes have a significant timing-based component. Plant-pollinator relationships, predator-prey interactions, and the distribution of species are just some of the aspects of ecosystems affected by phenology. And of critical importance today, human-induced climate change is altering phenology worldwide. In turn, many relationships and ecosystem functions will be impacted. In addition, phenological studies provide an excellent opportunity to bring ecology and education together. The collection of phenological data is labor intensive, and benefits greatly from the participation of volunteers. And nearly everyone can observe and appreciate phenology - people can see it in their own backyards, gardens, birdfeeders, and parks. Project BudBurst, a new citizen-science program in the US, highlights the benefits that citizen scientists and ecologists can provide one another. It follows the example of hugely popular citizen-scientist phenological monitoring programs in other parts of the world. This session features several case studies that show the vital role that citizen science can play in characterizing patterns of phenological change, and ways that phenological studies can contribute to the public’s understanding of climate change, ecology, and seasonal processes. It will also show some of the leading work to characterize the full complexity of phenological variability and change, particularly at the community level. The speakers will address phenology at several trophic levels and in a variety of ecosystems.