michael@0: /**
michael@0:  * Copyright (c) 2012, Ben Fortuna
michael@0:  * All rights reserved.
michael@0:  *
michael@0:  * Redistribution and use in source and binary forms, with or without
michael@0:  * modification, are permitted provided that the following conditions
michael@0:  * are met:
michael@0:  *
michael@0:  *  o Redistributions of source code must retain the above copyright
michael@0:  * notice, this list of conditions and the following disclaimer.
michael@0:  *
michael@0:  *  o Redistributions in binary form must reproduce the above copyright
michael@0:  * notice, this list of conditions and the following disclaimer in the
michael@0:  * documentation and/or other materials provided with the distribution.
michael@0:  *
michael@0:  *  o Neither the name of Ben Fortuna nor the names of any other contributors
michael@0:  * may be used to endorse or promote products derived from this software
michael@0:  * without specific prior written permission.
michael@0:  *
michael@0:  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
michael@0:  * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
michael@0:  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
michael@0:  * A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR
michael@0:  * CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
michael@0:  * EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
michael@0:  * PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
michael@0:  * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
michael@0:  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
michael@0:  * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
michael@0:  * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
michael@0:  */
michael@0: package net.fortuna.ical4j.util;
michael@0: 
michael@0: import java.util.TimeZone;
michael@0: 
michael@0: /**
michael@0:  * $Id$ [5/07/2004]
michael@0:  *
michael@0:  * Utility methods relevant to Java timezones.
michael@0:  *
michael@0:  * @author Ben Fortuna
michael@0:  */
michael@0: public final class TimeZones {
michael@0:     
michael@0:     /**
michael@0:      * The timezone identifier for UTC time.
michael@0:      */
michael@0:     public static final String UTC_ID = "Etc/UTC";
michael@0:     
michael@0:     /**
michael@0:      * The timezone identifier for UTC time in the IBM JVM.
michael@0:      */
michael@0:     public static final String IBM_UTC_ID = "GMT";
michael@0:     
michael@0:     /**
michael@0:      * The timezone identifier for GMT time.
michael@0:      */
michael@0:     public static final String GMT_ID = "Etc/GMT";
michael@0: 
michael@0:     private static final TimeZone UTC_TIMEZONE;
michael@0:     static {
michael@0:         UTC_TIMEZONE = TimeZone.getTimeZone(UTC_ID);
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Constructor made private to enforce static nature.
michael@0:      */
michael@0:     private TimeZones() {
michael@0:     }
michael@0:     
michael@0:     /**
michael@0:      * Indicates whether the specified timezone is equivalent to
michael@0:      * UTC time.
michael@0:      * @param timezone a timezone instance
michael@0:      * @return true if the timezone is UTC time, otherwise false
michael@0:      */
michael@0:     public static boolean isUtc(final TimeZone timezone) {
michael@0: //        return timezone.hasSameRules(TimeZone.getTimeZone(UTC_ID));
michael@0: //        return timezone.getRawOffset() == 0;
michael@0:         return UTC_ID.equals(timezone.getID())
michael@0:             || IBM_UTC_ID.equals(timezone.getID());
michael@0:     }
michael@0:     
michael@0:     /**
michael@0:      * Although timezones are not really applicable to DATE instances in iCalendar, the implementation
michael@0:      * in iCal4j requires the use of a timezone. Dates in iCal4j may be either "floating", in that they
michael@0:      * use the default Java timezone, or alternatively will use UTC (this is the default).
michael@0:      * 
michael@0:      * The use of floating dates may be configured by specifying the following as a system property or in
michael@0:      * a file called "ical4j.properties" in the classpath:
michael@0:      * 
michael@0:      * <pre>net.fortuna.ical4j.timezone.date.floating=true</pre>
michael@0:      * 
michael@0:      * @return the timezone used for date instances
michael@0:      */
michael@0:     public static TimeZone getDateTimeZone() {
michael@0:     	if ("true".equals(Configurator.getProperty("net.fortuna.ical4j.timezone.date.floating"))) {
michael@0:     		return TimeZone.getDefault();
michael@0:     	}
michael@0:     	return getUtcTimeZone();
michael@0:     }
michael@0: 
michael@0:     /**
michael@0:      * Get the UTC Timezone.
michael@0:      */
michael@0:     public static TimeZone getUtcTimeZone() {
michael@0:         return UTC_TIMEZONE;
michael@0:     }
michael@0: }