How can I uppercase each element of an array?

How can I turn an array of elements into uppercase? Expected output would be:

["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]  
=> ["MONDAY", "TUESDAY", "WEDNESDAY", "THURSDAY", "FRIDAY"]

The following didn't work and left them as lower case.

Day.weekday.map(&:name).each {|the_day| the_day.upcase }
 => ["Monday", "Tuesday", "Wednesday", "Thursday", "Friday"]