The ExcelChunkySAX library provides a way to process large Excel files in chunks using a SAX parser. It reads the Excel file in chunks and performs the specified action on each chunk. The library provides an interface ChunkAction that needs to be implemented to define the action to be performed on each chunk. The library uses Apache POI library to read the Excel file and SAX parser to parse the XML data. Note: any type of date format should be converted to yyyy-MM-dd.