If you want to practise, why not choose a month and see if you can crack it? And if you want to find, for example, a book cipher, why not click through a few until you find numbers?
(Warning: You may find I’ve been sneaky and used numbers for a substitution cipher. We need to be alert. Spies might be even sneakier than me.)
Summer Holidays Code
Summer Holiday Code Solution
Autumn 2016 Ciphers
December 2016 Christmas Carol Codes
Christmas 2017 Codes