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$dateToString (aggregation)

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  • Definition
  • Format Specifiers
  • Example
$dateToString

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

The $dateToString expression has the following operator expression syntax:

You can use $dateToString for deployments hosted in the following environments:

  • MongoDB Atlas: The fully managed service for MongoDB deployments in the cloud

The $dateToString expression has the following operator expression syntax:

{ $dateToString: {
date: <dateExpression>,
format: <formatString>,
timezone: <tzExpression>,
onNull: <expression>
} }
- The date to convert to string. ``<dateExpression>`` must be a
valid :ref:`expression <aggregation-expressions>` that
resolves to a :ref:`Date <document-bson-type-date>`, a
:ref:`Timestamp <document-bson-type-timestamp>`, or an
:ref:`ObjectID <document-bson-type-object-id>`.
* - Field
- Description
- Optional. The date format specification. ``<formatString>``
can be any string literal, containing 0 or more format
specifiers. For a list of specifiers available, see
:ref:`format-specifiers`.
If unspecified and the ``timezone`` is specified and set to a
non UTC timezone, then ``$dateToString`` uses
``"%Y-%m-%dT%H:%M:%S.%L"`` as the default format.
If unspecified and the ``timezone`` is unspecified or
explicitly specified as UTC, then ``$dateToString`` uses
``"%Y-%m-%dT%H:%M:%S.%LZ"`` as the default format.
The date to convert to string. ``<dateExpression>`` must be a
valid :ref:`expression <aggregation-expressions>` that
resolves to a :ref:`Date <document-bson-type-date>`, a
:ref:`Timestamp <document-bson-type-timestamp>`, or an
:ref:`ObjectID <document-bson-type-object-id>`.
* - ``format``
- Optional. The date format specification. ``<formatString>`` can be any
string literal, containing 0 or more format specifiers. For a
list of specifiers available, see :ref:`format-specifiers`.
If unspecified, :expression:`$dateToString` uses
``"%Y-%m-%dT%H:%M:%S.%LZ"`` as the default format.
If unspecified, ``$dateToString`` returns null if the
``date`` is null or missing.

Tip

See also:

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

Specifiers
Description
Possible Values
%b

Abbreviated month name (3 letters)

New in version 7.0.

jan-dec
%B

Full month name

New in version 7.0.

january-december
%d
Day of month (2 digits, zero padded)
01-31
%G
Year in ISO 8601 format
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)
1-7
%U
Week of year (2 digits, zero padded)
00-53
%V
Week of Year in ISO 8601 format
01-53
%w
Day of week (1-Sunday, 7-Saturday)
1-7
%Y
Year (4 digits, zero padded)
0000-9999
%z
The timezone offset from UTC.
+/-[hh][mm]
%Z
The minutes offset from UTC as a number. For example, if the timezone offset (+/-[hhmm]) was +0445, the minutes offset is +285.
+/-mmm
%%
Percent Character as a Literal
%

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 $dateToString to return the date field as formatted strings:

db.sales.aggregate(
[
{
$project: {
yearMonthDayUTC: { $dateToString: { format: "%Y-%m-%d", date: "$date" } },
timewithOffsetNY: { $dateToString: { format: "%H:%M:%S:%L%z", date: "$date", timezone: "America/New_York"} },
timewithOffset430: { $dateToString: { format: "%H:%M:%S:%L%z", date: "$date", timezone: "+04:30" } },
minutesOffsetNY: { $dateToString: { format: "%Z", date: "$date", timezone: "America/New_York" } },
minutesOffset430: { $dateToString: { format: "%Z", date: "$date", timezone: "+04:30" } },
abbreviated_month: { $dateToString: {format: "%b", date: "$date", timezone: "+04:30" } },
full_month: { $dateToString: { format: "%B", date: "$date", timezone: "+04:30" } }
}
}
]
)

The operation returns the following result:

{
"_id" : 1,
"yearMonthDayUTC" : "2014-01-01",
"timewithOffsetNY" : "03:15:39:736-0500",
"timewithOffset430" : "12:45:39:736+0430",
"minutesOffsetNY" : "-300",
"minutesOffset430" : "270",
"abbreviated_month": "Jan",
"full_month": "January"
}

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$dateTrunc (aggregation)