Past is free software for scientific data analysis, with functions for data manipulation, plotting, univariate and multivariate statistics, ecological analysis, time series and spatial analysis, morphometrics and stratigraphy. PAST integrates spreadsheet-type data entry with univariate and multivariate statistics, curve fitting, time-series analysis, data plotting, and simple phylogenetic analysis. Many of the functions are specific to paleontology and ecology, and these functions are not found in standard, more extensive, statistical packages. Past went through a complete redesign with version 3 in 2013. In 2020, version 4 was released with 64-bit support. Past works under Windows 7, Windows 10, and Mac OSX (including Catalina).