$dateToString (aggregation)¶

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Definition¶

$dateToString¶

New in version 3.0.

Converts a date object to a string according to a user-specified format.

The $dateToString expression has the following syntax:

{ $dateToString: { format: <formatString>, date: <dateExpression> } }

The $dateToString takes a document with the following fields:

Field	Description
`format`	The date format specification. `<formatString>` can be any string literal, containing 0 or more format specifiers. For a list of specifiers available, see Format Specifiers.
`date`	The date to convert to string. `<dateExpression>` can be any expression that evaluates to a date. For more information on expressions, see Expressions.

Format Specifiers¶

The following format specifiers are available for use in the <formatString>:

Specifiers	Description	Possible Values
`%d`	Day of Month (2 digits, zero padded)	`01`-`31`
`%G`	Year in ISO 8601 format New in version 3.4.	`0000`-`9999`
`%H`	Hour (2 digits, zero padded, 24-hour clock)	`00`-`23`
`%j`	Day of year (3 digits, zero padded)	`001`-`366`
`%L`	Millisecond (3 digits, zero padded)	`000`-`999`
`%m`	Month (2 digits, zero padded)	`01`-`12`
`%M`	Minute (2 digits, zero padded)	`00`-`59`
`%S`	Second (2 digits, zero padded)	`00`-`60`
`%u`	Day of week number in ISO 8601 format (1-Monday, 7-Sunday) New in version 3.4.	`1`-`7`
`%U`	Week of year (2 digits, zero padded)	`00`-`53`
`%V`	Week of Year in ISO 8601 format New in version 3.4.	`1`-`53`
`%w`	Day of week (1-Sunday, 7-Saturday)	`1`-`7`
`%Y`	Year (4 digits, zero padded)	`0000`-`9999`
`%%`	Percent Character as a Literal	`%`

Example¶

Consider a sales collection with the following document:

{
  "_id" : 1,
  "item" : "abc",
  "price" : 10,
  "quantity" : 2,
  "date" : ISODate("2014-01-01T08:15:39.736Z")
}

The following aggregation uses the $dateToString to return the date field as formatted strings:

db.sales.aggregate(
   [
     {
       $project: {
          yearMonthDayUTC: { $dateToString: { format: "%Y-%m-%d", date: "$date" } },
          time: { $dateToString: { format: "%H:%M:%S:%L", date: "$date" } }
       }
     }
   ]
)

The operation returns the following result:

{ "_id" : 1, "yearMonthDayUTC" : "2014-01-01", "time" : "08:15:39:736" }

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