One of the earliest weather datasets, the Test Reference Year (TRY), was created with historical weather data from 1948 to 1975. TRY was limited because it did not contain actual solar data, and the data selection process excluded all weather extremes, resulting in a mild representative year. In light of these shortcomings, a new dataset, the Typical Meteorological Year (TMY), emerged in 1981, including actual solar radiation values. TMY is the preferred dataset used by many simulation engines today. The methodology used to create a TMY dataset is similar to the TRY but with one key difference. TMY uses the most typical months instead of isolating the most typical year. For example, data for January might be sourced from 1996, while data for May comes from 2017.