The article presents a review of studies that have experimentally shown that a sudden increase in the photoperiod duration or the use of abnormal light-dark cycles when growing plants under artificial climate conditions causes photoperiod stress. Similarly to other types of stress, it induces a whole range of changes and/or disturbances in plants, which may add up to become fatal. As studies show, photoperiod stress increases the generation of ROS in plants, resulting in the development of oxidative stress. However, if the stress is not too strong (mild or moderate), then the induced nonspecific resistance mechanisms help the plants retain viability and successfully survive the stressful period. Importantly, the consequences of such stress are not necessarily negative. Moreover, by manipulating photoperiod length it is possible to identify those that, although fundamentally abnormal for plants, are nevertheless capable of exerting a positive effect in terms of improving some economically important indices, in particular those that determine the nutritional value and biosafety (due to a decrease in nitrate content) of plant products. Consequently, even if photoperiod stress is generally harmful for plants, it can still be useful for humans in achieving the intended economic result, whether it is increased yield, higher quality (better consumer characteristics), or reduced costs per unit produce.