Calendar anomalies as an example of interferences of the efficient market hypothesis – pandemic and post-pandemic economic reality

The purpose of this paper is to review the state of research about calendar effects as an example of biases in the efficient market hypothesis carried out in the era of pandemic and post-pandemic economic reality (2020–2023). Based on the method of reviewing and critical analysis of the literature, a summary of the previous state of research on the issue of calendar effects conducted in 2020–2023 was prepared. Drawing on research results coming from different corners of the world, it is still possible to recognize the occurrence of calendar anomalies in the vast majority of them in accordance with their previous correlations. As can be seen, the increase in uncertainty has not led to the disappearance of the occurrence of the majority of calendar anomalies. Reviewing the state of research, a certain research gap was also noticed, which concerns the failure to address the topic of calendar effects in the era of post-pandemic economic reality, accompanied by Russia’s armed aggression against Ukraine.