How to Change a Discrete Field Label in Tableau

The other day I received an interesting request on our The Information Lab support desk from a customer who wanted to change the default label of a discrete date. In this case he displayed a bar chart with the week number as a label, but he was constrained on space and wanted to alter the label from for example 'Week 1' to 'wk 1'. However, when you try to reformat this label, Tableau just doesn't do it. There might be a valid reason for this but I thought I should be able to. There are probably many ways to do this but in the video below I explain how I approached this issue and how I tackled it.