# $dateFromParts (aggregation)

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## Definition

`$dateFromParts`

Constructs and returns a Date object given the date's constituent properties.

The

`$dateFromParts`

expression has the following syntax:{ $dateFromParts : { 'year': <year>, 'month': <month>, 'day': <day>, 'hour': <hour>, 'minute': <minute>, 'second': <second>, 'millisecond': <ms>, 'timezone': <tzExpression> } } You can also specify your constituent date fields in ISO week date format using the following syntax:

{ $dateFromParts : { 'isoWeekYear': <year>, 'isoWeek': <week>, 'isoDayOfWeek': <day>, 'hour': <hour>, 'minute': <minute>, 'second': <second>, 'millisecond': <ms>, 'timezone': <tzExpression> } } The

`$dateFromParts`

takes a document with the following fields:## Important

You cannot combine the use of calendar dates and ISO week date fields when constructing your

`$dateFromParts`

input document.FieldRequired/OptionalDescription`year`

Required if not using`isoWeekYear`

Calendar year. Can be any expression that evaluates to a number.

Value range:

If the number specified is outside this range,`1`

-`9999`

`$dateFromParts`

errors. The lower bound for this value is`1`

.`isoWeekYear`

Required if not using`year`

ISO Week Date Year. Can be any expression that evaluates to a number.

Value range:

If the number specified is outside this range,`1`

-`9999`

`$dateFromParts`

errors. The lower bound for this value is`1`

.`month`

Optional. Can only be used with`year`

.Month. Can be any expression that evaluates to a number.

Defaults to

`1`

.Value range:

If the number specified is outside this range,`1`

-`12`

`$dateFromParts`

incorporates the difference in the date calculation. See Value Range for examples.`isoWeek`

Optional. Can only be used with`isoWeekYear`

.Week of year. Can be any expression that evaluates to a number.

Defaults to

`1`

.Value range:

If the number specified is outside this range,`1`

-`53`

`$dateFromParts`

incorporates the difference in the date calculation. See Value Range for examples.`day`

Optional. Can only be used with`year`

.Day of month. Can be any expression that evaluates to a number.

Defaults to

`1`

.Value range:

If the number specified is outside this range,`1`

-`31`

`$dateFromParts`

incorporates the difference in the date calculation. See Value Range for examples.`isoDayOfWeek`

Optional. Can only be used with`isoWeekYear`

.Day of week (Monday

`1`

- Sunday`7`

). Can be any expression that evaluates to a number.Defaults to

`1`

.Value range:

If the number specified is outside this range,`1`

-`7`

`$dateFromParts`

incorporates the difference in the date calculation. See Value Range for examples.`hour`

OptionalHour. Can be any expression that evaluates to a number.

Defaults to

`0`

.Value range:

If the number specified is outside this range,`0`

-`23`

`$dateFromParts`

incorporates the difference in the date calculation. See Value Range for examples.`minute`

OptionalMinute. Can be any expression that evaluates to a number.

Defaults to

`0`

.Value range:

`0`

-`59`

If the number specified is outside this range,`$dateFromParts`

incorporates the difference in the date calculation. See Value Range for examples.`second`

OptionalSecond. Can be any expression that evaluates to a number.

Defaults to

`0`

.Value range:

If the number specified is outside this range,`0`

-`59`

`$dateFromParts`

incorporates the difference in the date calculation. See Value Range for examples.`millisecond`

OptionalMillisecond. Can be any expression that evaluates to a number.

Defaults to

`0`

.Value range:

If the number specified is outside this range,`0`

-`999`

`$dateFromParts`

incorporates the difference in the date calculation. See Value Range for examples.`timezone`

Optional`<timezone>`

can be any expression that evaluates to a string whose value is either:an Olson Timezone Identifier, such as

`"Europe/London"`

or`"America/New_York"`

, ora UTC offset in the form:

`+/-[hh]:[mm]`

, e.g.`"+04:45"`

, or`+/-[hh][mm]`

, e.g.`"-0530"`

, or`+/-[hh]`

, e.g.`"+03"`

.

For more information on expressions, see Expression Operators.

## Behavior

### Value Range

The supported value range for `year`

and `isoWeekYear`

is `1-9999`

.

If the value specified for fields other than `year`

, `isoWeekYear`

,
and `timezone`

is outside the valid range, `$dateFromParts`

carries or subtracts the difference from other date parts to calculate
the date.

### Value is Greater than the Range

Consider the following `$dateFromParts`

expression where
the `month`

field value is `14`

, which is 2 months greater than the
maximum value of 12 months(or 1 year):

{ $dateFromParts: { 'year' : 2017, 'month' : 14, 'day': 1, 'hour' : 12 } }

The expression calculates the date by increasing the `year`

by 1
and setting the `month`

to 2 to return:

ISODate("2018-02-01T12:00:00Z")

### Value is Less than the Range

Consider the following `$dateFromParts`

expression where
the `month`

field value is `0`

, which is 1 month less than the
minimum value of 1 month:

{ $dateFromParts: { 'year' : 2017, 'month' : 0, 'day': 1, 'hour' : 12 } }

The expression calculates the date by decreasing the `year`

by 1
and setting the `month`

to 12 to return:

ISODate("2016-12-01T12:00:00Z")

### Time Zone

When using an Olson Timezone Identifier in the `<timezone>`

field, MongoDB applies the DST offset
if applicable for the specified timezone.

For example, consider a `sales`

collection with the following document:

{ "_id" : 1, "item" : "abc", "price" : 20, "quantity" : 5, "date" : ISODate("2017-05-20T10:24:51.303Z") }

The following aggregation illustrates how MongoDB handles the DST
offset for the Olson Timezone Identifier. The example uses the
`$hour`

and `$minute`

operators to return the
corresponding portions of the `date`

field:

db.sales.aggregate([ { $project: { "nycHour": { $hour: { date: "$date", timezone: "-05:00" } }, "nycMinute": { $minute: { date: "$date", timezone: "-05:00" } }, "gmtHour": { $hour: { date: "$date", timezone: "GMT" } }, "gmtMinute": { $minute: { date: "$date", timezone: "GMT" } }, "nycOlsonHour": { $hour: { date: "$date", timezone: "America/New_York" } }, "nycOlsonMinute": { $minute: { date: "$date", timezone: "America/New_York" } } } }])

The operation returns the following result:

{ "_id": 1, "nycHour" : 5, "nycMinute" : 24, "gmtHour" : 10, "gmtMinute" : 24, "nycOlsonHour" : 6, "nycOlsonMinute" : 24 }

## Example

The following aggregation uses `$dateFromParts`

to
construct three date objects from the provided input fields:

db.sales.aggregate([ { $project: { date: { $dateFromParts: { 'year' : 2017, 'month' : 2, 'day': 8, 'hour' : 12 } }, date_iso: { $dateFromParts: { 'isoWeekYear' : 2017, 'isoWeek' : 6, 'isoDayOfWeek' : 3, 'hour' : 12 } }, date_timezone: { $dateFromParts: { 'year' : 2016, 'month' : 12, 'day' : 31, 'hour' : 23, 'minute' : 46, 'second' : 12, 'timezone' : 'America/New_York' } } } }])

The operation returns the following result:

{ "_id" : 1, "date" : ISODate("2017-02-08T12:00:00Z"), "date_iso" : ISODate("2017-02-08T12:00:00Z"), "date_timezone" : ISODate("2017-01-01T04:46:12Z") }