public String getPreferredMaintenanceWindow() {
        return this.preferredMaintenanceWindow;
    }
<p>
The weekly time range during which system maintenance can occur on your database.
</p>
<p>
The default is a 30-minute window selected at random from an 8-hour block of time for each Amazon Web Services
Region, occurring on a random day of the week.
</p>
<p>
Constraints:
</p>
<ul>
<li>
<p>
Must be in the <code>ddd:hh24:mi-ddd:hh24:mi</code> format.
</p>
</li>
<li>
<p>
Valid days: Mon, Tue, Wed, Thu, Fri, Sat, Sun.
</p>
</li>
<li>
<p>
Must be at least 30 minutes.
</p>
</li>
<li>
<p>
Specified in Coordinated Universal Time (UTC).
</p>
</li>
<li>
<p>
Example: <code>Tue:17:00-Tue:17:30</code>
</p>
</li>
</ul>

@return The weekly time range during which system maintenance can occur on your database.</p>
        <p>
        The default is a 30-minute window selected at random from an 8-hour block of time for each Amazon Web
        Services Region, occurring on a random day of the week.
        </p>
        <p>
        Constraints:
        </p>
        <ul>
        <li>
        <p>
        Must be in the <code>ddd:hh24:mi-ddd:hh24:mi</code> format.
        </p>
        </li>
        <li>
        <p>
        Valid days: Mon, Tue, Wed, Thu, Fri, Sat, Sun.
        </p>
        </li>
        <li>
        <p>
        Must be at least 30 minutes.
        </p>
        </li>
        <li>
        <p>
        Specified in Coordinated Universal Time (UTC).
        </p>
        </li>
        <li>
        <p>
        Example: <code>Tue:17:00-Tue:17:30</code>
        </p>
        </li>
aws-java-sdk-lightsail/src/main/java/com/amazonaws/services/lightsail/model/UpdateRelationalDatabaseRequest.java