restygwt/src/main/java/org/fusesource/restygwt/client/Defaults.java
public static void setDateFormat(String dateFormat) {
        Defaults.dateFormat = dateFormat;
        dateFormatHasTimeZone = false;

        if (dateFormat != null) {
            for (int i = 0; i < dateFormat.length(); i++) {
                char ch = dateFormat.charAt(i);

                if (ch == 'Z' || ch == 'z' || ch == 'V' || ch == 'v') {
                    dateFormatHasTimeZone = true;
                    break;
                }
            }
        }
    }
public static void setDateFormat(String dateFormat) {
        Defaults.dateFormat = dateFormat;
        dateFormatHasTimeZone = false;

        if (dateFormat != null) {
            for (int i = 0; i < dateFormat.length(); i++) {
                char ch = dateFormat.charAt(i);

                if (ch == 'Z' || ch == 'z' || ch == 'V' || ch == 'v') {
                    dateFormatHasTimeZone = true;
                    break;
                }
            }
        }
    }
Sets the format used when encoding and decoding Dates. If the date
format is set to {@code null}, dates will be encoded and decoded as
timestamps (the number of milliseconds since the Unix epoch,
1970-01-01).

@param dateFormat the date format string
@see com.google.gwt.i18n.shared.DateTimeFormat DateTimeFormat