By Sreekesh Eyyapadi, Technical Lead, CRG Solutions
There are many date functions in Tableau. Some manipulate dates, some convert data to dates, some identify if data is a date. This article will run through the main date functions and give some usage examples
- Finding the latest date in the data source
{MAX([OrderDate])}
This formula will return the maximum date and is also usable in other calculations. It’ll appear in the list of available Dimensions for use elsewhere.
- The Tableau ISDATE function – is my date field recognised as a date?
ISDATE([Field])
To test which values are recognised by Tableau as being a valid date, use the ISDATE() function. The function is boolean, it returns True for records identified as dates and False for those Tableau doesn’t think are dates.
- Identify the latest month
DATETRUNC(‘month’,{MAX([OrderDate])})
This formula finds the latest date in the dataset, then sets that date to the first of the month.
- Identify the same month last year
DATEADD(‘year’,-1,DATETRUNC(‘month’,{MAX([OrderDate])}))
Similar to above, but this time also incorporate a DATEADD to find the same month last year.
- First day of current month
DATE(DATETRUNC(‘month’, [Date]))
- Last day of current month
DATE(DATEADD(‘day’, -1, DATEADD(‘month’, 1, DATETRUNC(‘month’, [Date]))))
- First day of next month
DATE(DATEADD(‘month’, 1,DATETRUNC(‘month’, [Date]))
- Last day of next month
DATE(DATEADD(‘day’, -1, DATEADD(‘month’, 2, DATETRUNC(‘month’, [Date]))))
- First day of previous month
DATE(DATEADD(‘month’, -1,DATETRUNC(‘month’, [Date]))
- Last day of previous month
DATE(DATEADD(‘day’, -1, DATETRUNC(‘month’, [Date])))
- Fiscal year calculation (Apr – Mar)
if datepart(‘year’,dateadd(‘month,9,Date))=2024 then ‘FY2024’ end
- Week number start at 1 for every new month
int(datepart(‘day’,[Date])/7)+1
- Days since beginning of the quarter
DATEDIFF(‘day’, DATETRUNC(‘quarter’, TODAY(), TODAY()))
This is a practical application of DATETRUNC, when we need to calculate pro-rata amount. For example, usually Quarterly Target is provided and our data holds Sales at daily transaction level. To check if our current Sales is on track, number of days since beginning of the Quarter can be used to compute proportional Target and then matched with Sales amount so far in this quarter.
With little tweaks here and there we can similarly define other date calculations as well.
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