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This paper reports on the development of a new computerized calculation methodology for determining the Arrhenius Time Weighted Average Temperature for the purpose of determining the qualified life of components in an environmental qualification (EQ) program. The methodology is based on the new technique published in IEEE Standard 1205-2000 . The project assessed numerous temperature averaging and weighting techniques to determine relative accuracy and conservatism. The selected averaging technique enhances accuracy relative to other techniques and ensures the generation of conservative results in all cases with respect to a "real time" Arrhenius average temperature. The methodology was used to process a very large quantity of containment temperature data and to produce Arrhenius time-weighted average temperature curves for equipment, based both on containment elevation and activation energy. The methodology accounts for outages and seasonal temperature fluctuations, and can be periodically updated as additional temperature data becomes available.