In addition to this list, the SQL plugin also supports the `datetime` type, though it doesn't have a corresponding mapping with OpenSearch or SQL.
To use a function without a corresponding mapping, you must explicitly convert the data type to one that does.
## Date and time types
The date and time types represent a time period: `DATE`, `TIME`, `DATETIME`, `TIMESTAMP`, and `INTERVAL`. By default, the OpenSearch DSL uses the `date` type as the only date-time related type that contains all information of an absolute time point.
To integrate with SQL, each type other than the `timestamp` type holds part of the time period information. To use date-time functions, see [datetime]({{site.url}}{{site.baseurl}}/search-plugins/sql/functions#date-and-time). Some functions might have restrictions for the input argument type.
The `date` type represents the calendar date regardless of the time zone. A given date value is a 24-hour period, but this period varies in different timezones and might have flexible hours during daylight saving programs. The `date` type doesn't contain time information and it only supports a range of `1000-01-01` to `9999-12-31`.
| Type | Syntax | Range
:--- | :--- | :---
date | `yyyy-MM-dd` | `0001-01-01` to `9999-12-31`
### Time
The `time` type represents the time of a clock regardless of its timezone. The `time` type doesn't contain date information.
The `datetime` type is a combination of date and time. It doesn't contain timezone information. For an absolute time point that contains date, time, and timezone information, see [Timestamp](#timestamp).
The `timestamp` type is an absolute instance independent of timezone or convention. For example, for a given point of time, if you change the timestamp to a different timezone, its value changes accordingly.
The `timestamp` type is stored differently from the other types. It's converted from its current timezone to UTC for storage and converted back to its set timezone from UTC when it's retrieved.
The `expr` unit is any expression that eventually iterates to a quantity value. It represents a unit for interpreting the quantity, including `MICROSECOND`, `SECOND`, `MINUTE`, `HOUR`, `DAY`, `WEEK`, `MONTH`, `QUARTER`, and `YEAR`. The `INTERVAL` keyword and the unit specifier are not case sensitive.
The `interval` type has two classes of intervals: year-week intervals and day-time intervals.
- Year-week intervals store years, quarters, months, and weeks.
- Day-time intervals store days, hours, minutes, seconds, and microseconds.
### Convert between date and time types
Apart from the `interval` type, all date and time types can be converted to each other. The conversion might alter the value or cause some information loss. For example, when extracting the `time` value from a `datetime` value, or converting a `date` value to a `datetime` value, and so on.
The SQL plugin supports the following conversion rules for each of the types:
**Convert from date**
- Because the `date` value doesn't have any time information, conversion to the `time` type isn't useful and always returns a zero time value of `00:00:00`.
- Converting from `date` to `datetime` has a data fill-up due to the lack of time information. It attaches the time `00:00:00` to the original date by default and forms a `datetime` instance. For example, conversion of `2020-08-17` to a `datetime` type is `2020-08-17 00:00:00`.
- Converting to `timestamp` type alternates both the `time` value and the `timezone` information. It attaches the zero time value `00:00:00` and the session timezone (UTC by default) to the date. For example, conversion of `2020-08-17` to a `datetime` type with a session timezone UTC is `2020-08-17 00:00:00 UTC`.
**Convert from time**
- You cannot convert the `time` type to any other date and time types because it doesn't contain any date information.
**Convert from datetime**
- Converting `datetime` to `date` extracts the date value from the `datetime` value. For example, conversion of `2020-08-17 14:09:00` to a `date` type is `2020-08-08`.
- Converting `datetime` to `time` extracts the time value from the `datetime` value. For example, conversion of `2020-08-17 14:09:00` to a `time` type is `14:09:00`.
- Because the `datetime` type doesn't contain timezone information, converting to `timestamp` type fills up the timezone value with the session timezone. For example, conversion of `2020-08-17 14:09:00` (UTC) to a `timestamp` type is `2020-08-17 14:09:00 UTC`.
**Convert from timestamp**
- Converting from a `timestamp` type to a `date` type extracts the date value and converting to a `time` type extracts the time value. Converting from a `timestamp` type to `datetime` type extracts only the `datetime` value and leaves out the timezone value. For example, conversion of `2020-08-17 14:09:00` UTC to a `date` type is `2020-08-17`, to a `time` type is `14:09:00`, and to a `datetime` type is `2020-08-17 14:09:00`.
