Free desktop clocks often include multiple skin options, date displays, 12- and 24-hour formats, alarm features, time zone selection and resizing capabilities. Many desktop clock programs are designed to simply adapt the existing clock already on the computer by adding new features instead of replacing it outright.
Clock skins allow users to change the overall appearances of the clocks. They are typically not customizable, but they offer multiple different looks and colors so users can pick their favorites. Some clocks allow for multiple alarms to be set simultaneously, and some allow for alarms to repeat so they go off daily or weekly. The sound or tone may be variable or customizable. The specific details vary from program to program, so users need to always read about the features and functions of specific clock programs before downloading and installing them.
While some free clock apps automatically sync to the current time zone, time and date, others require the information to be entered manually, meaning the time needs to be re-entered when the clocks change during Daylight Saving Time. The 12-hour clock is usually standard, but most programs allow for users to switch to "military time," or a 24-hour cycle.
Free programs often include additional functions that are undesired or harmful, so users should always research programs and read reviews about them before installing them on their hard drives to avoid virus or malware exposure.