Why do a clock not keep correct time in summer?

A clock may not keep correct time in summer due to the practice of Daylight Saving Time, where clocks are set forward by one hour to make better use of daylight. This adjustment can lead to confusion if people forget to change their clocks or if they don’t account for the time shift. Additionally, variations in temperature can affect mechanical clocks, causing them to run fast or slow. Thus, improper timekeeping during summer can result from both human error and physical factors.