Which command is used to display current date and time in Linux?

The command used to display the current date and time in Linux is "date." When you execute this command in a terminal, it retrieves and displays the system's current date and time in a user-friendly format. The functionality provided by the "date" command goes beyond just displaying the current date and time; it can also be formatted to show various components of the date, perform date arithmetic, and display dates in different time zones, among other features.

The other options listed do not fulfill the purpose of showing the current date and time in the same way. "time" is typically used to measure how long a command takes to run, while "datetime" and "now" are not standard commands in Linux. Hence, "date" is the correct command for this task.