IOSACal is an open source program for calibration of radiocarbon dates. This release brings the new IntCal20 calibration data and several improvements for different use cases, plus one important bug fix. the project has moved to Codeberg for source code hosting and issue tracking. The new Git repository is at https://codeberg.org/steko/iosacal with a default branch name of main there is an official Code of Conduct that all contributors (including the maintainter) will need to follow the documentation has seen some improvements, in particular in the Contributing section. Overall, making contributions easier from both expert and novice users is a major theme in this release. interactive use in Jupyter notebooks is made easier with CalibrationCurve that can be created in many ways (such as loading from an arbitrary file, or from a standard calibration curve called by shorthand) fixed a bug that made plots with AD/CE setting incorrect (contributed by Karl Håkansson) fixed a bug that caused a wrong plot density function for dates 80 BP to 0 BP (contributed by Karl Håkansson) add IntCal20 calibration data (contributed by Wesley Weatherbee) On the technical side: the command line interface is now based on the Click library most code is now covered by tests, based on pytest Python 3.6 or above required requires Numpy 1.18 and Matplotlib 3.0