1. A method comprising: generating, using a processor, an event representation of an image collection; computing global time-based features for each event within a hierarchical event representation; computing image-level content-based features for each image in an event within the hierarchical event representation; combining image-level content-based features for each image in an event to generate event-level content-based features; classifying, using time-based features including at least one of a duration of event, inter-event duration, or number of images in the event and event-level content-based features, each event into a category from a pre-determined set of top-level event categories; and validating, using a rule-based system, each event belongs to an associated category based on the event-level content-based features; and refining the category of at least one event into a sub-category based on the event-level content-based features.