Bug 202121 setDateFormat does not working
If you want to set date format of the table column style you have to use setDateTimeFormatCategory and setDateTimeFormat instead of setDateFormatCategory and setDateFormat. If you will try to use setDateFormatCategory in the first case in xml-source you will see that your style contains dateFormat property. This property is not working at all, in the second case in xml-source you will see that your style contains dateTimeFormat property. I think it will be better if the result of setDateTimeFormatCategory and setDateFormatCategory will be the same.
engine/org.eclipse.birt.report.engine/src/org/eclipse/birt/report/engine/css/dom/AbstractStyle.java
/*******************************************************************************
 * Copyright (c) 2004 Actuate Corporation.
 * All rights reserved. This program and the accompanying materials
 * are made available under the terms of the Eclipse Public License v1.0
 * which accompanies this distribution, and is available at
 * http://www.eclipse.org/legal/epl-v10.html
 *
 * Contributors:
 *  Actuate Corporation  - initial API and implementation
 *******************************************************************************/
package org.eclipse.birt.report.engine.css.dom;
import org.eclipse.birt.report.engine.content.IStyle;
import org.eclipse.birt.report.engine.css.engine.CSSEngine;
import org.w3c.dom.DOMException;
import org.w3c.dom.css.CSSPrimitiveValue;
import org.w3c.dom.css.CSSRule;
import org.w3c.dom.css.CSSValue;
abstract public class AbstractStyle implements IStyle