Calendar wake up is a start action and is used to activate your server from standby (not from Shutdown).

Enable uptime start, enter a time value (1) and tick the "Wake up from suspension or hibernation" option (2). 

This action is executed as a single action (3) on the selected day (see dialog caption), or repeated on the selected days of the week (4).

A calendar wake-up requires that your server is in standby. It does not work from shutdown!

Calendar page tab