One of the main problems in knowledge representation is checking consistency. In the paper under review, the consistency of temporal knowledge is considered, i.e., of knowledge about moments and intervals of time that correspond to different events. The authors show that even if we consider only knowledge consisting of the statements "intervals $[a^-,a^+]$ and $[b^-,b^+]$ are disjoint" and "moment $a$ precedes moment $b$" (i.e., $a