The First Day of the Week

Overview

By default, the first day of the week depends on the locale (e.g., Sunday in US, Monday in France). More precisely, it is the value returned by the getFirstDayOfWeek method of the java.util.Calendar class.

However, you can configure it differently, and it will affect how datebox and calendar components behave.

The decision sequence of the first day of the week

The first day of the week is decided in the following sequence.

1. It checks if an attribute called org.zkoss.web.preferred.firstDayOfWeek is defined in the HTTP session (aka., Session). If so, use it.
2. It checks if an attribute called org.zkoss.web.preferred.firstDayOfWeek is defined in the Servlet context (aka., Application). If so, use it.
3. It checks if a property called org.zkoss.web.preferred.firstDayOfWeek is defined in the library property (i.e., Library). If so, use it.
4. If none of them is found, JVM's default will be used (java.util.Calendar).

Application-level first-day-of-the-week

Since 5.0.3

If you want to use the same first-day-of-the-week for all users of the same application, you can specify it in the library property. The allowed values include 1 (Sunday), 2 (Monday), .. and 7 (Saturday). For example, you could specify the following in WEB-INF/zk.xml:

<library-property>
    <name>org.zkoss.web.preferred.firstDayOfWeek</name>
    <value>7</value><!-- Saturday -->
</library-property>

Alternatively, if you prefer to specify it in Java, you could invoke Library.setProperty(String, String). Furthermore, to avoid typos, you could use WebApp.setAttribute(String, Object) and Attributes.PREFERRED_FIRST_DAY_OF_WEEK as follows.

webApp.setAttribute(org.zkoss.web.Attributes.PREFERRED_FIRST_DAY_OF_WEEK, java.util.Calendar.SATURDAY);

As shown above, the allowed values of WebApp.setAttribute(String, Object) include Calendar.SUNDAY, Calendar.MONDAY and so on.

Per-user first-day-of-week

Since 5.0.3

By specifying a value to the session attribute called org.zkoss.web.preferred.firstDayOfWeek (i.e., Attributes.PREFERRED_FIRST_DAY_OF_WEEK), you can control the first day of the week for the given session. The allowed values include Calendar.SUNDAY, Calendar.MONDAY and so on.

session.setAttribute(org.zkoss.web.Attributes.PREFERRED_FIRST_DAY_OF_WEEK, java.util.Calendar.SATURDAY);
  //then, the current session's first day of the week will be Saturday

For example, you can do this when a user logins.

 void login(String username, String password) {
     //check password
     ...
     int preferredFDOW = ...; //decide the user's preference
     session.setAttribute(Attributes.PREFERRED_FIRST_DAY_OF_WEEK, preferredFDOW);
...