Dates are a common element in many data sources. If a field contains recognizable dates, it will have a date or date time data type. When date fields are used in the viz they get a special set of functionality, including an automatic date hierarchy drill down, date-specific filter options, and specialized date formatting options.

Date functions allow you to manipulate dates in your data source.

Date Functions

Date functions sometimes reference date-specific elements, including the date_part argument, the optional [start_of_week] parameter, and date literals (#). These are covered in more detail at the end of this topic.

There are several other topics that might be of interest but aren't part of date functions:

DATE

Type conversion function that changes string and number expressions into dates, as long as they are in a recognizable format.

Syntax DATE(expression)
Output Date
Definition Returns a date given a number, string, or date expression.
Example
DATE([Employee Start Date])
DATE("September 22, 2018") 
DATE("9/22/2018")
DATE(#2018-09-22 14:52#)
Notes

Unlike DATEPARSE, there is no need to provide a pattern as DATE automatically recognizes many standard date formats. If DATE does not recognize the input, however, try using DATEPARSE and specifying the format.

MAKEDATE is another similar function, but MAKEDATE requires the input of numeric values for year, month, and day.

DATEADD

Adds a specified number of date parts (months, days, etc) to the starting date.

Syntax DATEADD(date_part, interval, date)
Output Date
Definition Returns the specified date with the specified number interval added to the specified date_part of that date. For example, adding three months or 12 days to a starting date.
Example

Push out all due dates by one week

DATEADD('week', 1, [due date])

 

Add 280 days to the date February 20, 2021

DATEADD('day', 280, #2/20/21#) = #November 27, 2021#
Notes Supports ISO 8601 dates.

DATEDIFF

Returns the number of date parts (weeks, years, etc) between two dates.

Syntax DATEDIFF(date_part, date1, date2, [start_of_week])
Output Integer
Definition Returns the difference between date1 and date2 expressed in units of date_part. For example, subtracting the dates someone entered and left a band to see how long they were in the band.
Example

Number of days between March 25, 1986 and February 20, 2021

DATEDIFF('day', #3/25/1986#, #2/20/2021#) = 12,751

 

How many months someone was in a band

DATEDIFF('month', [date joined band], [date left band])
Notes Supports ISO 8601 dates.

DATENAME

Returns the name of the specified date part as a discrete string.

Syntax DATENAME(date_part, date, [start_of_week])
Output String
Definition Returns date_part of date as a string.
Example
DATENAME('year', #3/25/1986#) = "1986"
DATENAME('month', #1986-03-25#) = "March"
Notes

Supports ISO 8601 dates.

A very similar calculation is DATEPART, which returns the value of the specified date part as a continuous integer. DATEPART can be faster because it is a numerical operation.

By changing the attributes of the calculation’s result (dimension or measure, continuous or discrete) and the date formatting, the results of DATEPART and DATENAME can be formatted to be identical.

An inverse function is DATEPARSE, which takes a string value and formats it as a date.

DATEPARSE

Returns specifically formatted strings as dates.

Syntax DATEPARSE(date_format, [date_string])
Output Date
Definition The date_format argument will describe how the [string] field is arranged. Because of the variety of ways the string field can be ordered, the date_format must match exactly. For a full explanation, see Convert a Field to a Date Field.
Example
DATEPARSE('yyyy-MM-dd', "1986-03-25") = #March 25, 1986#
Notes

DATE is a similar function that automatically recognizes many standard date formats. DATEPARSE may be a better option if DATE does not recognize the input pattern.

MAKEDATE is another similar function, but MAKEDATE requires the input of numeric values for year, month, and day.

Inverse functions, which take dates apart and return the value of their parts, are DATEPART (integer output) and DATENAME (string output).

Database limitations

DATEPARSE is available through the following connectors: non-legacy Excel and text file connections, Amazon EMR Hadoop Hive, Cloudera Hadoop, Google Sheets, Hortonworks Hadoop Hive, MapR Hadoop Hive, MySQL, Oracle, PostgreSQL, and Tableau extracts. Some formats may not be available for all connections.

DATEPARSE is not supported on Hive variants. Only Denodo, Drill, and Snowflake are supported.

DATEPART

Returns the name of the specified date part as an integer.

Syntax DATEPART(date_part, date, [start_of_week])
Output Integer
Definition Returns date_part of date as an integer.
Example
DATEPART('year', #1986-03-25#) = 1986
DATEPART('month', #1986-03-25#) = 3
Notes

Supports ISO 8601 dates.

A very similar calculation is DATENAME, which returns the name of the specified date part as a discrete string. DATEPART can be faster because it is a numerical operation. By changing the attributes of the field (dimension or measure, continuous or discrete) and the date formatting, the results of DATEPART and DATENAME can be formatted to be identical.

An inverse function is DATEPARSE, which takes a string value and formats it as a date.

DATETRUNC

This function can be thought of as date rounding. It takes a specific date and returns a version of that date at the desired specificity. Because every date must have a value for day, month, quarter, and year, DATETRUNC sets the values as the lowest value for each date part up to the date part specified. Refer to the example for more information.

Syntax DATETRUNC(date_part, date, [start_of_week])
Output Date
Definition Truncates the date to the accuracy specified by the date_part. This function returns a new date. For example, when you truncate a date that is in the middle of the month at the month level, this function returns the first day of the month.
Example
DATETRUNC(‘day’, #9/22/2018#) = #9/22/2018#
DATETRUNC(‘week’, #9/22/2018#) = #9/16/2018# 

(the sunday of the week containing 9/22/2018)

DATETRUNC(‘iso-week’, #9/22/2018#) = #9/17/2018#      

(the monday of the week containing 9/22/2018)

DATETRUNC(month, #9/22/2018#) = #9/1/2018#      

(the first day of the month containing 9/22/2018)

DATETRUNC(quarter, #9/22/2018#) = #7/1/2018# 

(the first day of the quarter containing 9/22/2018)

DATETRUNC(‘week’, #9/22/2018#) = #1/1/2018#      

(the first day of the year containing 9/22/2018)

Note: For week and iso-week, the start_of_week comes into play. ISO-weeks always start on Monday. For the locale of this example, an unspecified start_of_week means the week starts on Sunday.

Notes

Supports ISO 8601 dates.

You would not use DATETRUNC to, for example, stop showing the time for a datetime field in a viz. If you want to truncate the display of a date rather than round its accuracy, adjust the formatting.

For example, DATETRUNC('day', #5/17/2022 3:12:48 PM#), if shown in the viz to the second, would display as 5/17/2022 12:00:00 AM.

DAY

Returns the day of the month (1-31) as an integer.

Syntax DAY(date)
Output Integer
Definition Returns the day of the given date as an integer.
Example
Day(#September 22, 2018#) = 22
Notes See also WEEK, MONTH, QUARTER, YEAR, and the ISO equivalents

ISDATE

Checks if the string is a valid date format.

Syntax ISDATE(string)
Output Boolean
Definition Returns true if a given string is a valid date.
Example
ISDATE(09/22/2018) = true
ISDATE(22SEP18) = false
Notes The required argument must be a string. ISDATE cannot be used for a field with a date data type—the calculation will return an error.

MAKEDATE

Syntax MAKEDATE(year, month, day)
Output Date
Definition Returns a date value constructed from the specified year, month, and date.
Example
MAKEDATE(1986,3,25) = #1986-03-25#

Note that incorrectly entered values will be adjusted into a date, such as MAKEDATE(2020,4,31) = May 1, 2020 rather than returning an error that there is no 31st day of April.

Notes

Available for Tableau Data Extracts. Check for availability in other data sources.

MAKEDATE requires numerical inputs for the parts of a date. If your data is a string that should be a date, try the DATE function. DATE automatically recognizes many standard date formats. If DATE does not recognize the input try using DATEPARSE.

MAKEDATETIME

Syntax MAKEDATETIME(date, time)
Output Datetime
Definition Returns a datetime that combines a date and a time. The date can be a date, datetime, or a string type. The time must be a datetime.
Example
MAKEDATETIME("1899-12-30", #07:59:00#) = #12/30/1899 7:59:00 AM#
MAKEDATETIME([Date], [Time]) = #1/1/2001 6:00:00 AM#
Notes

This function is available only for MySQL-compatible connections (which for Tableau are MySQL and Amazon Aurora).

MAKETIME is a similar function available for Tableau Data Extracts and some other data sources.

MAKETIME

Syntax MAKETIME(hour, minute, second)
Output Datetime
Definition Returns a date value constructed from the specified hour, minute, and second.
Example
MAKETIME(14, 52, 40) = #1/1/1899 14:52:40#
Notes

Because Tableau does not support a time data type, only date time, the output is a a datetime. The date portion of the field will be 1/1/1899.

Similar function to MAKEDATETIME, which is only available for MYSQL-compatible connections.

MAX

Syntax MAX(expression) or MAX(expr1, expr2)
Output Date (see notes)
Definition MAX is usually applied to numbers but also works on dates. Returns the maximum (most recent) of a date field or two dates.
Example
MAX(#Sept 22, 2018#, #Feb 20, 2021#) = #Feb 20, 2021#
MAX([Ship date])
Notes

MAX(expression) is treated as an aggregate function and returns a single aggregated result. This will display as AGG([calculation name]) in the viz and will not have a date hierarchy.

MAX(expr1, expr2) compares the two values and returns a row-level value. For dates, that value will be a date, and the results will retain the date hierarchy.

Returns Null if any argument is Null.

MIN

Syntax MIN(expression) or MIN(expr1, expr2)
Output Date (see notes)
Definition MIN is usually applied to numbers but also works on dates. Returns the minimum (earliest) of a date field or two dates.
Example
MIN(#Sept 22, 2018#, #Feb 20, 2021#) = #Sept 22, 2018#
MIN(Ship date])
Notes

MIN(expression) is treated as an aggregate function and returns a single aggregated result. This will display as AGG([calculation name]) in the viz and will not have a date hierarchy.

MIN(expr1, expr2) compares the two values and returns a row-level value. For dates, that value will be a date, and the results will retain the date hierarchy.

Returns Null if any argument is Null.

MONTH

Syntax MONTH(date)
Output Integer
Definition Returns the month of the given date as an integer.
Example
MONTH(#1986-03-25#) = 3
Notes See also DAY, WEEK, QUARTER, YEAR, and the ISO equivalents.

NOW

Syntax NOW()
Output Datetime
Definition Returns the current local system date and time.
Example
NOW() = 1986-03-25 1:08:21 PM
Notes

NOW does not take an argument.

See also TODAY, a similar calculation that returns a date instead of a datetime.

If the data source is a live connection, the system date and time could be in another timezone. For more information on how to address this, see the Knowledge Base.

QUARTER

Syntax QUARTER(date)
Output Integer
Definition Returns the quarter of the given date as an integer.
Example
QUARTER(#1986-03-25#) = 1
Notes See also DAY, WEEK, MONTH, YEAR, and the ISO equivalents.

TODAY

Syntax TODAY()
Output Date
Definition Returns the current local system date.
Example
TODAY() = 1986-03-25
Notes

TODAY does not take an argument.

See also NOW, a similar calculation that returns a datetime instead of a date.

If the data source is a live connection, the system date could be in another timezone. For more information on how to address this, see the Knowledge Base.

WEEK

Syntax WEEK(date)
Output Integer
Definition Returns the week of the given date as an integer.
Example
WEEK(#1986-03-25#) = 13
Notes See also DAY, MONTH, QUARTER, YEAR, and the ISO equivalents.

YEAR

Syntax YEAR(date)
Output Integer
Definition Returns the year of the given date as an integer.
Example
YEAR(#1986-03-25#) = 1,986
Notes See also DAY, WEEK, MONTH, QUARTER, and the ISO equivalents.

ISOQUARTER

Syntax ISOQUARTER(date)
Output Integer
Definition Returns the ISO8601 week-based quarter of a given date as an integer.
Example
ISOQUARTER(#1986-03-25#) = 1
Notes See also ISOWEEK, ISOWEEKDAY, ISOYEAR, and the non-ISO equivalents.

ISOWEEK

Syntax ISOWEEK(date)
Output Integer
Definition Returns the ISO8601 week-based week of a given date as an integer.
Example
ISOWEEK(#1986-03-25#) = 13
Notes See also ISOWEEKDAY, ISOQUARTER, ISOYEAR, and the non-ISO equivalents.

ISOWEEKDAY

Syntax ISOWEEKDAY(date)
Output Integer
Definition Returns the ISO8601 week-based weekday of a given date as an integer.
Example
ISOWEEKDAY(#1986-03-25#) = 2
Notes See also ISOWEEK, ISOQUARTER, ISOYEAR, and the non-ISO equivalents

ISOYEAR

Syntax ISOYEAR(date)
Output Integer
Definition Returns the ISO8601 week-based year of a given date as an integer.
Example
ISOYEAR(#1986-03-25#) = 1,986
Notes See also ISOWEEK, ISOWEEKDAY, ISOQUARTER, and the non-ISO equivalents.

The date_part argument

Many date functions in Tableau take the argument date_part, which is a string constant that tells the function what part of a date to consider, such as day, week, quarter, etc.

The valid date_part values that you can use are:

date_part Values
'year' Four-digit year
'quarter' 1-4
'month' 1-12 or "January", "February", and so on
'dayofyear' Day of the year; Jan 1 is 1, Feb 1 is 32, and so on
'day' 1-31
'weekday' 1-7 or "Sunday", "Monday", and so on
'week' 1-52
'hour' 0-23
'minute' 0-59
'second' 0-60
'iso-year' Four-digit ISO 8601 year
'iso-quarter' 1-4
'iso-week' 1-52, start of week is always Monday
'iso-weekday' 1-7, start of week is always Monday

The [start_of_week] parameter

Some functions have the optional parameter [start_of_week]. The start_of_week parameter can be used to specify what day is considered the first day of the week, such as "Sunday" or "Monday". If it is omitted, the start of week is determined by the data source. See Date Properties for a Data Source.

For the examples below, 22 September is a Sunday and 24 September is a Tuesday. The DATEDIFF function is being used to calculate the weeks between these dates.

DATEDIFF('week', #2013-09-22#, #2013-09-24#, 'monday') = 1

  • Because start_of_week is 'monday', these dates are in different weeks.

DATEDIFF('week', #2013-09-22#, #2013-09-24#, 'sunday') = 0

  • Because start_of_week is 'sunday', these dates are in the same week.

The date literal (#)

Examples often use the pound symbol (#) with date expressions. This is the date literal, similar to using quotes for text strings, and it tells Tableau that the value inside the symbols is a date.

Without the date literals, dates may be interpreted as various other data types. For example:

Format Data Type Value
'March 25, 1986' String 'March 25, 1986'
#3/25/1986# Date #3/25/1986#
03/25/1986 Floating decimal 0.00006042
1986-03-25 Integer 1,958
March 25, 1986   invalid

For more information, see Literal expression syntax

Create a date calculation

Practice creating a date calculation using the Superstore sample data source.

  1. In Tableau Desktop, connect to the Sample-Superstore saved data source, which comes with Tableau.
  2. Open a worksheet.
  3. From the Data pane, under Dimensions, drag Order Date to the Rows shelf.
  4. On the Rows shelf, click the plus icon (+) on the YEAR(Order Date) field.

    QUARTER(Order Date) is added to the Rows shelf and the view updates.

  5. On the Rows shelf, click the plus icon (+) on the QUARTER(Order Date) field to drill down to MONTH(Order Date).

  6. Select Analysis > Create Calculated Field.
  7. In the calculation editor that opens, do the following:
    • Name the calculated field, Quarter Date.
    • Enter the following formula: DATETRUNC('quarter', [Order Date])
    • When finished, click OK.

      The new date calculated field appears under Dimensions in the Data pane. Just like your other fields, you can use it in one or more visualizations.

  8. From the Data pane, under Dimensions, drag Quarter Date to the Rows shelf and place it to the right of MONTH(Order Date). The visualization updates with year values. This is because Tableau rolls date data up to the highest level of detail.
  9. On the Rows shelf, right-click YEAR(Quarter Date) and select Exact Date.
  10. On the Rows shelf, right-click YEAR(Quarter Date) again and select Discrete.

    The visualization updates with the exact quarter date for each row in the table.

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