The Light Development Holiday Library is a Java class library that models any kind of holiday as an event in the gregorian calendar system. It simplifies the high complexity of holiday definition by matching all different holiday classes against the same single common interface taking away the need to know about each and every detail of computation, calendar systems and algorithms.

The library models nine different holiday classes over the four calendar systems gregorian, islamic, hebrew and chinese. The combination of classes (i.e. computation methods) and calendar systems already models holidays observerd by the majority of world population.

Additional support for Buddhist, Hindu, Julian, Orthodox and Coptic calendar systems and holidays is in preparation, making the Holiday Library the most comprehensive and common tool for modeling and occurence determination of holidays.