All ecological relationships and ecosystem processes can be characterized in terms of change over time. Phenology is the study of the timing of recurring biological events, the interaction of biotic and abiotic factors affecting these events, and the interrelation among temporal phases of the same or different species. In recent years there has been widespread renewed interest in phenological research, largely due to the importance of phenology in detecting climate change and made evident by the efforts of the USA National Phenology Network (USA-NPN) to coordinate phenological monitoring among environmental agencies, scientific networks, and professional and citizen scientists. The applications of phenology research extend far beyond climate change and include optimizing the timing of agricultural practices; predicting the onset and intensity of economically-important allergens, pests, and pollinators; planning recreational and ecotourism ventures; and forecasting natural phenomena such as wildfire and disease spread. Since phenology is an interdisciplinary science that integrates multiple biological and geographical scales, many professional and citizen scientists collect phenological data but with different, potentially complementary, goals. However, a variety of analytical techniques are employed at each scale and interpretations of phenological patterns vary (particularly evident at ESA 2008). This session features researchers who interpret phenological patterns and characterize the causes and consequences of phenological variation. Data from professional and citizen scientists will be presented. Speakers will provide insight into data structure and choice of analytical methods, including anova, multiple regression, selection gradient, Bayesian, multivariate, and geospatial. This session will provide insight into the methods by which this burgeoning multidisciplinary field is quantifying natural variation across biological, geographical, and temporal scales.