Tableau Prep: Up & Running

Chapter 8. Dealing with Dates

Sorry to anyone looking for dating advice—this chapter isn’t for you. For those who are battling dates in their data sets, it is for you! In this chapter we will explore why dates are important in the world of data, how to break up dates, what different types of dates you might come across and need to prepare, and how to use date functions in Prep Builder to clean up your dates so they’re ready for analysis.

Why Are Dates Important?

A basic date field can start to tell us so much:

• How many sales were made on Saturday?

• How many students joined the program this term?

• How many games does my team play this month?

We can begin to answer all of these by counting the number of rows and breaking them down by the different parts of the date.

Parts of a Date

When most of us think of dates, we think of days, months, and years. Which side of the Atlantic Ocean we are on generally determines whether the months or days are listed first. As I am British, the rest of this chapter (and book) will unapologetically place days in front of months.

The date format we commonly use is dd/MM/yyyy (e.g., 25/09/2019). The d represents the day of the month; we use dd as there are potentially two digits for the day. M stands for month, and again MM is used because there are potentially two digits in the month. The y is for year, and you’ll use either two digits for the last two digits of the year, represented by yy (e.g., 19 for the date in Figure 8-1), or four digits ...