[[esql-time-spans]]
=== {esql} time spans

++++
<titleabbrev>Time spans</titleabbrev>
++++

Time spans represent intervals between two datetime values. There are currently two supported types of time spans:

* `DATE_PERIOD` specifies intervals in years, quarters, months, weeks and days
* `TIME_DURATION` specifies intervals in hours, minutes, seconds and milliseconds

A time span requires two elements: an integer value and a temporal unit.

Time spans work with grouping functions such as <<esql-bucket, BUCKET>>, scalar functions such as <<esql-date_trunc, DATE_TRUNC>> and arithmetic operators such as <<esql-add, `+`>> and <<esql-subtract, `-`>>. Convert strings to time spans using <<esql-to_dateperiod, TO_DATEPERIOD>>, <<esql-to_timeduration, TO_TIMEDURATION>>, or the cast operators `::DATE_PERIOD`, `::TIME_DURATION`.

[discrete]
[[esql-time-spans-examples]]
==== Examples of using time spans in {esql}


With `BUCKET`:
[source.merge.styled,esql]
----
include::{esql-specs}/bucket.csv-spec[tag=docsBucketWeeklyHistogramWithSpan]
----
[%header.monospaced.styled,format=dsv,separator=|]
|===
include::{esql-specs}/bucket.csv-spec[tag=docsBucketWeeklyHistogramWithSpan-result]
|===


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


With `+` and/or `-`:
[source.merge.styled,esql]
----
include::{esql-specs}/date.csv-spec[tag=docsNowWhere]
----
[%header.monospaced.styled,format=dsv,separator=|]
|===
include::{esql-specs}/date.csv-spec[tag=docsNowWhere-result]
|===


When a time span is provided as a named parameter in string format, `TO_DATEPERIOD`, `::DATE_PERIOD`, `TO_TIMEDURATION` or `::TIME_DURATION` can be used to convert to its corresponding time span value for arithmetic operations like `+` and/or `-`.
[source, esql]
----
POST /_query
{
   "query": """
   FROM employees
   | EVAL x = hire_date + ?timespan::DATE_PERIOD, y = hire_date - TO_DATEPERIOD(?timespan)
   """,
   "params": [{"timespan" : "1 day"}]
}
----

When a time span is provided as a named parameter in string format, it can be automatically converted to its corresponding time span value in grouping functions and scalar functions, like `BUCKET` and `DATE_TRUNC`.
[source, esql]
----
POST /_query
{
   "query": """
   FROM employees
   | WHERE hire_date >= "1985-01-01T00:00:00Z" AND hire_date < "1986-01-01T00:00:00Z"
   | STATS hires_per_week = COUNT(*) BY week = BUCKET(hire_date, ?timespan)
   | SORT week
   """,
   "params": [{"timespan" : "1 week"}]
}
----

[source, esql]
----
POST /_query
{
   "query": """
   FROM employees
   | KEEP first_name, last_name, hire_date
   | EVAL year_hired = DATE_TRUNC(?timespan, hire_date)
   """,
   "params": [{"timespan" : "1 year"}]
}
----

[discrete]
[[esql-time-spans-table]]
==== Supported temporal units
[%header.monospaced.styled,format=dsv,separator=|]
|===
Temporal Units|Valid Abbreviations
year|y, yr, years
quarter|q, quarters
month|mo, months
week|w, weeks
day|d, days
hour|h, hours
minute|min, minutes
second|s, sec, seconds
millisecond|ms, milliseconds
|===
