[discrete]
[[esql-to_datetime]]
=== `TO_DATETIME`

*Alias*

`TO_DT`

*Syntax*

[source,esql]
----
TO_DATETIME(v)
----

*Parameters*

`v`::
Input value. The input can be a single- or multi-valued column or an expression.

*Description*

Converts an input value to a date value.

A string will only be successfully converted if it's respecting the format
`yyyy-MM-dd'T'HH:mm:ss.SSS'Z'`. To convert dates in other formats, use
<<esql-date_parse>>.

*Supported types*

The input type must be of a string or numeric type.

*Examples*

[source.merge.styled,esql]
----
include::{esql-specs}/date.csv-spec[tag=to_datetime-str]
----
[%header.monospaced.styled,format=dsv,separator=|]
|===
include::{esql-specs}/date.csv-spec[tag=to_datetime-str-result]
|===

Note that in this example, the last value in the source multi-valued
field has not been converted. The reason being that if the date format is not
respected, the conversion will result in a *null* value. When this happens a
_Warning_ header is added to the response. The header will provide information
on the source of the failure:

`"Line 1:112: evaluation of [TO_DATETIME(string)] failed, treating result as null. Only first 20 failures recorded."`

A following header will contain the failure reason and the offending value:

`"java.lang.IllegalArgumentException: failed to parse date field [1964-06-02 00:00:00] with format [yyyy-MM-dd'T'HH:mm:ss.SSS'Z']"`

If the input parameter is of a numeric type, its value will be interpreted as
milliseconds since the {wikipedia}/Unix_time[Unix epoch]. For example:

[source.merge.styled,esql]
----
include::{esql-specs}/date.csv-spec[tag=to_datetime-int]
----
[%header.monospaced.styled,format=dsv,separator=|]
|===
include::{esql-specs}/date.csv-spec[tag=to_datetime-int-result]
|===