What command is used to check the current date and time on a Linux system?

The command used to check the current date and time on a Linux system is "date." When you execute this command in the terminal, it retrieves and displays the system’s current date and time according to the configured time zone. This command can also be used with various options to format the output according to specific requirements, such as displaying just the time or the date in different formats.

The other options listed as choices do not correspond to valid commands in the Linux environment for checking the date and time. Thus, while "currenttime," "datetime," and "today" may seem like they could be appropriate, they do not exist as standard commands in Linux. Therefore, "date" is the correct and only valid choice for this purpose.