R package seasonal. Easy-to-use interface to X-13-ARIMA-SEATS, the seasonal adjustment software by the US Census Bureau. It offers full access to almost all options and outputs of X-13, including X-11 and SEATS, automatic ARIMA model search, outlier detection and support for user defined holiday variables, such as Chinese New Year or Indian Diwali. It also includes a Shiny-based graphical user interface. Seasonal uses the X-13 binaries from the ’x13binary’ package.