Welcome to this special issue of the Journal of Scheduling. We are delighted to present you with a selection of peer reviewed papers from the submissions to the 13th International Conference on the Practice and Theory of Automated Timetabling (PATAT) in 2020 and 2021. The PATAT conference series has been running biennially, since 1995, when the very first conference was organised in Edinburgh. As its name suggests, PATAT is concerned with all aspects of the Practice and Theory of Automated Timetabling. The conference series has taken the theoretical developments in combinatorial optimisation to application in a broad range of areas, including high-school and university timetabling, healthcare and sports.

PATAT has brought structure to the description of problems in each of these domains by supporting various competitions and challenges. The first three International Timetabling Competition (ITC) series were organised on educational timetabling, including the variants of course, examination and high-school timetabling problems. ITCs have taken algorithmic performance in those various application domains to significantly improved levels. Apart from stimulating the design of approaches with improved performance, ITCs have ignited the development of new formats for specifying relevant problems, setting the paradigms. The ITC example was followed by the Cross-domain Heuristic Search Challenge and International Nurse Rostering Competition line. More recently, two competitions were organised, one on university course timetabling (ITC 2019) and another one on sports timetabling (ITC 2021). In addition, PATAT has dramatically demonstrated the capacity of, and need for, heuristic approaches for building effective solvers while increasing modelling power. Equally important is PATAT’s engagement with practitioners. Every edition of the conference has offered a platform for companies and developers to demonstrate their software and to go into discussion with academic researchers. Above all, PATAT has created an international community of participants from across the world, allowing and stimulating them to present and discuss problems, to exchange experiences, to bring in and study the application of new scientific and technological developments, to offer training opportunities for PhD students, and to enable our worldwide community to move forward.

The 2020 edition of PATAT was to mark the silver anniversary of the PATAT conference series. It was meant to be held in Belgium in August 2020. Due to the COVID-19 crisis, the event had to be postponed twice. We will see what the near future brings and to what extent the very social and interactive event that we have known will take place. In the meantime, researchers have been conducting research, producing excellent results. This special issue draws upon the fruits of their work that was peer-reviewed, appeared in the first two volumes of the online proceedings and accepted for presentation at the postponed 13th PATAT conferences.

We would like to express our gratitude to the PATAT Programme Committee members for their complete and rigorous reviews. We also thank the Steering Committee for their hard work and ongoing support for the successful continuation of the PATAT conference series. Finally, we extend our gratitude to all the authors and delegates for their contributions to the conference and competitions.