Simple Summary: Cancer significantly affects physical and mental health, evoking intense emotions and forcing life changes. Emotional responses to cancer treatment have an intrinsic connection with time, in particular with the positive memories of how life looked before the disease and the often grim and hopeless outlook on the future. This study found that patients in chemotherapy experience increased focus on the present, decreased focus on the future, and a sense of unpredictability, with a relatively short temporal horizon measured in weeks and months, not years. These experiences are prevalent regardless of the type of cancer, the length of treatment, and the sociodemographic background. It can be concluded that changed temporal experience during chemotherapy is a factor that can have an impact on patients' well-being and ability to cope with the disease. Understanding the impact of cancer on the experience of time is crucial in the context of hope and recovery. This study, a follow-up to a previous qualitative study of ovarian cancer patients – explored two types of such experiences—the memory of past happiness and the limited future planning. A sociodemographic questionnaire with nine questions about the experience of time was used on a convenience sample of 202 patients with various cancers, predominantly women with breast, ovarian, and cervical cancer. It was found that the respondents experienced increased focus on the present, decreased focus on the future, and a sense of unpredictability, with a relatively short temporal horizon measured in weeks and months, not years. Almost half of the respondents (46%) measured time during treatment by the rhythm of chemotherapy and check-ups, which thus appeared as the most meaningful events. The increase in the frequency with which patients underwent chemotherapy mildly affected their focus on the present (R = 0.25, p < 0.05), likely because of the discomfort of the side effects. The correlations between age and time in treatment, on the one hand, and the experience of time, on the other, were negligible. Changed temporal experience during chemotherapy is a factor that can have an impact on patients' well-being and ability to cope with the disease. It thus should be taken into account when planning oncology care. [ABSTRACT FROM AUTHOR]