How to set the oracle time format

The time format in Oracle databases can be set through session-level or system-level settings. Session-level settings have higher priority than system-level settings. Oracle supports a variety of time formats, such as "YYYY-MM-DD HH24:MI:SS" and "DD-MON-YY HH:MI:SS AM/PM". Session-level settings can be performed by the ALTER SESSION command or the PL/SQL TO_CHAR function; system-level settings can be performed by setting the NLS_DATE_FORMAT parameter in the init.ora or spfile.ora file.

Oracle Time Format Settings

In Oracle database, the time format can be set in the following ways:

Session-level settings

• Use ALTER SESSION command:

 <code class="sql">ALTER SESSION SET NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS';</code>

• Use the PL/SQL TO_CHAR function:

 <code class="sql">SELECT TO_CHAR(sysdate, 'YYYY-MM-DD HH24:MI:SS') FROM dual;</code>

System-level settings

• Set the NLS_DATE_FORMAT parameter in init.ora or spfile.ora configuration file:

 <code>NLS_DATE_FORMAT = 'YYYY-MM-DD HH24:MI:SS'</code>

• Restart the Oracle service to apply the changes.

Priority for session and system level settings

• Session-level settings have higher priority than system-level settings.
• If the time format is not set in the session, use the system level settings.

Supported time formats

Oracle supports a variety of time formats, including:

• YYYY-MM-DD HH24:MI:SS (ISO 8601)
• DD-MON-YY HH:MI:SS AM/PM
• YY-MM-DD HH:MI:SS
• HH:MI:SS
• DD MON YYYY

Other precautions

• Certain functions and procedures may require specific time formats.
• When using the TIMESTAMP data type, the timestamp is stored in the local time zone, so it may be necessary to apply a time zone transformation to display the correct time zone time.

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