Date calculations (DATEDIFF, DATEADD) in Tableau - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to calculate the number of days between Order Date and Ship Date.

Tableau

DATEDIFF('day', [Order Date], [1])

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ATODAY()

B[Order Date]

C[Ship Date]

DNOW()

Attempts:

3 left

💡 Hint

Common Mistakes

Using [Order Date] twice, which results in zero difference.

Using TODAY() or NOW() which gives difference from current date, not Ship Date.

DATEDIFF calculates the difference between two dates. Here, we want days between Order Date and Ship Date, so Ship Date is the second argument.

2fill in blank

medium

Complete the code to add 3 months to the Order Date.

Tableau

DATEADD('month', [1], [Order Date])

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A3

B1

C-3

D12

Attempts:

3 left

💡 Hint

Common Mistakes

Using 1 or 12 which adds wrong number of months.

Using negative number which subtracts months.

DATEADD adds a specified number of intervals to a date. To add 3 months, use 3 as the second argument.

3fill in blank

hard

Fix the error in the code to calculate the number of weeks between two dates.

Tableau

DATEDIFF([1], [Start Date], [End Date])

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A'weeks'

B'week'

Cweek

Dweeks

Attempts:

3 left

💡 Hint

Common Mistakes

Omitting quotes around the interval.

Using plural form 'weeks' which is invalid.

The interval argument in DATEDIFF must be a string in single quotes, like 'week'.

4fill in blank

hard

Fill both blanks to calculate the date 10 days before the Ship Date.

Tableau

DATEADD([1], [2], [Ship Date])

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A'day'

B-10

C10

D'month'

Attempts:

3 left

💡 Hint

Common Mistakes

Using positive number which adds days instead of subtracting.

Using wrong interval like 'month' instead of 'day'.

To subtract days, use 'day' as the interval and a negative number for days to subtract.

5fill in blank

hard

Fill all three blanks to calculate the number of months between Order Date and Ship Date, then add 2 months to the Order Date.

Tableau

DATEDIFF([1], [Order Date], [Ship Date]) + DATEADD([2], [3], [Order Date])

Drag options to blanks, or click blank then click option'

A'month'

B'day'

C2

D-2

Attempts:

3 left

💡 Hint

Common Mistakes

Using different intervals for DATEDIFF and DATEADD.

Using negative number to add months.

Mixing up the order of dates in DATEDIFF.

Use 'month' as interval for DATEDIFF and DATEADD. Add 2 months by using 2 as the number.

Practice

1. What does the Tableau function DATEDIFF('day', #2024-01-01#, #2024-01-10#) return?

easy

A. 10

B. 11

C. 9

D. Error

Solution

1. Step 1: Understand DATEDIFF parameters

   DATEDIFF counts the number of boundaries crossed between two dates in the specified unit, here 'day'.

2. Step 2: Calculate days between 2024-01-01 and 2024-01-10

   From Jan 1 to Jan 10, there are 9 full days difference, but DATEDIFF counts the number of day boundaries crossed, which is 10 (Jan 1 to Jan 2 is 1, ... Jan 9 to Jan 10 is 9, plus the starting boundary counts as well).

3. Final Answer:

   10 -> Option A

4. Quick Check:

   DATEDIFF('day', start, end) counts days crossed = 10 [OK]

Hint: DATEDIFF counts boundaries crossed, not total days [OK]

Common Mistakes:

• Counting both start and end dates as full days
• Confusing DATEDIFF with DATEADD
• Using wrong unit like 'month' instead of 'day'

2. Which of the following is the correct syntax to add 3 months to a date field [Order Date] in Tableau?

easy

A. DATEADD([Order Date], 3, 'month')

B. DATEADD('3 months', [Order Date])

C. DATEDIFF('month', [Order Date], 3)

D. DATEADD('month', 3, [Order Date])

Solution

1. Step 1: Recall DATEADD syntax

   DATEADD takes three arguments: date part as string, number to add, and the date field.

2. Step 2: Match correct argument order

   DATEADD('month', 3, [Order Date]) matches syntax: DATEADD('month', 3, [Order Date]). Others have wrong order or wrong function.

3. Final Answer:

   DATEADD('month', 3, [Order Date]) -> Option D

4. Quick Check:

   Correct DATEADD syntax = DATEADD('month', 3, [Order Date]) [OK]

Hint: DATEADD('unit', number, date) is the correct order [OK]

Common Mistakes:

• Swapping argument order
• Using DATEDIFF instead of DATEADD
• Passing units as part of number argument

3. What is the result of this Tableau calculation?
DATEDIFF('week', #2024-01-01#, DATEADD('day', 15, #2024-01-01#))

medium

A. 2

B. 3

C. 1

D. 0

Solution

1. Step 1: Calculate DATEADD('day', 15, #2024-01-01#)

   Adding 15 days to Jan 1, 2024 results in Jan 16, 2024.

2. Step 2: Calculate DATEDIFF in weeks between Jan 1 and Jan 16

   Weeks crossed: Jan 1 to Jan 8 (1 week), Jan 8 to Jan 15 (2 weeks), Jan 15 to Jan 16 does not complete another week. So total 2 weeks difference.

3. Final Answer:

   2 -> Option A

4. Quick Check:

   DATEDIFF('week', start, end) counts full weeks crossed = 2 [OK]

Hint: Add days first, then count weeks crossed [OK]

Common Mistakes:

• Counting partial weeks as full weeks
• Mixing up order of DATEADD and DATEDIFF
• Using wrong date formats

4. You wrote this Tableau formula but it gives an error:
DATEADD('day', '5', [Ship Date])
What is the problem?

medium

A. The date field [Ship Date] must be a string

B. The date part 'day' should be in uppercase

C. The number of days should not be in quotes

D. DATEADD cannot add days, only months

Solution

1. Step 1: Check argument types in DATEADD

   DATEADD expects the second argument as a number, not a string.

2. Step 2: Identify error cause

   Using '5' (string) instead of 5 (number) causes a type error.

3. Final Answer:

   The number of days should not be in quotes -> Option C

4. Quick Check:

   Number argument must be numeric, not string [OK]

Hint: Numbers in DATEADD must be numeric, no quotes [OK]

Common Mistakes:

• Putting numbers in quotes
• Assuming case sensitivity for 'day'
• Thinking DATEADD only works with months

5. You want to find how many full quarters have passed between #2023-02-15# and a date 200 days later. Which Tableau formula correctly calculates this?

hard

A. DATEDIFF('month', #2023-02-15#, DATEADD('day', 200, #2023-02-15#)) / 3

B. DATEDIFF('quarter', #2023-02-15#, DATEADD('day', 200, #2023-02-15#))

C. DATEDIFF('quarter', DATEADD('day', 200, #2023-02-15#), #2023-02-15#)

D. DATEADD('quarter', 200, #2023-02-15#)

Solution

1. Step 1: Calculate the date 200 days after Feb 15, 2023

   Using DATEADD('day', 200, #2023-02-15#) gives the target date.

2. Step 2: Use DATEDIFF with 'quarter' to count full quarters passed

   DATEDIFF('quarter', start_date, end_date) counts how many quarter boundaries are crossed.

3. Step 3: Evaluate options

   DATEDIFF('quarter', #2023-02-15#, DATEADD('day', 200, #2023-02-15#)) correctly uses DATEDIFF with 'quarter' and correct date order. DATEDIFF('month', #2023-02-15#, DATEADD('day', 200, #2023-02-15#)) / 3 divides months by 3 but may give decimals, not full quarters. DATEDIFF('quarter', DATEADD('day', 200, #2023-02-15#), #2023-02-15#) reverses dates causing negative result. DATEADD('quarter', 200, #2023-02-15#) misuses DATEADD.

4. Final Answer:

   DATEDIFF('quarter', #2023-02-15#, DATEADD('day', 200, #2023-02-15#)) -> Option B

5. Quick Check:

   Use DATEDIFF('quarter', start, end) for full quarters [OK]

Hint: Use DATEDIFF with 'quarter' and correct date order [OK]

Common Mistakes:

• Dividing months by 3 instead of using 'quarter'
• Swapping start and end dates
• Using DATEADD instead of DATEDIFF for difference