opensearch-docs-cn/_opensearch/date_math_support.md

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Date math support for index names

Date math is shorthand arithmetic for finding relative dates.

If you're indexing time-series data with the dates mapped in the index names, you can use date math in your queries to filter index names and limit the number of searched indices.

Date math syntax

The date math syntax for an index name is as follows:

<static_name{date_math_expr{date_format|time_zone}}>

• static_name: The unchanged or static portion of the index name. To use the characters { and } in the static part of an index name, escape them with a backslash \.
• date_math_expr: The changing or dynamic portion of the index name that’s computed by the date math expression. For example, now+1h adds one hour, now-1d subtracts one hour, and now/d rounds down to the nearest day, where now represents the current timestamp.
• date_format: (Optional) Specify the format for the computed date. The default value is YYYY.MM.dd. Make sure that you’re using the correct small or capital letters in the date format. For example, mm denotes minute of hour, while MM denotes month of year. Similarly, hh denotes the hour in the 1-12 range in combination with AM/PM, while HH denotes the hour in the 0-23 24-hour range.
• time_zone: (Optional) Specify the timezone offset. The default value is UTC. For example, the UTC time offset for PST is -08:00.

Date math example

You must enclose date math index names within angle brackets.

If today is 22nd March, 2024:

• <logstash-{now/d}> resolves to logstash-2024.03.22
• <logstash-{now/M}> resolves to logstash-2024.03.01
• <logstash-{now/M{YYYY.MM}}> resolves to logstash-2024.03
• <logstash-{now/M-1M{YYYY.MM}}> resolves to logstash-2024.02
• <logstash-{now/d{yyyy.MM.dd|+12:00}}> resolves to logstash-2024.03.23

You need to encode all special characters in URI format:

Special characters	URI format
<	%3C
>	%3E
/	%2F
{	%7B
}	%7D
`	`
+	%2B
:	%3A
,	%2C
\	%5C

If you are searching for errors in your daily logs with the default Logstash index name format logstash-YYYY.MM.dd, you can use date math to restrict the search to indices of the past three days:

# GET <logstash-{now/d-2d}>,<logstash-{now/d-1d}>,<logstash-{now/d}>/_search
GET %3Clogstash-%7Bnow%2Fd-2d%7D%3E%2C%3Clogstash-%7Bnow%2Fd-1d%7D%3E%2C%3Clogstash-%7Bnow%2Fd%7D%3E/_search

This date math expression is evaluated at runtime.