#Google RFC 2445

This is a mavenized version of the google-rfc-2455 project on Google Code.

##Purpose

RFC 2445 describes a scheme for calendar interoperability. This project implements core parts of RFC 2445 including a parser for recurrence rules, and date lists, and a mechanism for evaluating recurrence rules.

Features:

• evaluates recurrence rules that don't occur more frequently than daily
• evaluates groups of recurrence rules and handles exceptions
• Support for Joda-time dates and java.util.Date

To-Do:

• Direct support for recurrences more frequent than daily
• Support for user-defined timezones

Requirements:

• JDK 1.5

Maturity: Stable -- deployed in a large scale calendaring application Efficient for all common recurrences and reasonably efficient for others (Run tests for micro-benchmarks) No known non-halting behaviors

##Support

For questions and the occasional answer, join the user & developer group.

Online Documentation

The javadoc is available online.

Building

Prerequisites:

• Java JDK 7 or higher
• Maven 3

To build the jar:

git clone https://github.com/jcvanderwal/google-rfc-2445.git
git checkout mavenized
mvn clean install -DskipTests

The original project contains some failing tests, to be fixed.

Using

Add this dependency to your project's pom.xm

<dependency>
    <groupId>com.google</groupId>
    <artifactId>rfc-2445</artifactId>
    <version>1.0-SNAPSHOT</version>
</dependency>

Using the API is pretty easy. Pass in some ical and you get back a date iterable, which can be used in a for-each loop thusly:

// A compatibility layer for joda-time
import com.google.ical.compat.jodatime.LocalDateIteratorFactory;
// A Joda time class that represents a day regardless of timezone
import org.joda.time.LocalDate;

public class ThirteenFridaysTheThirteenth {

  /** print the first 13 Friday the 13ths in the 3rd millenium AD. */
  public static void main(String[] args) throws java.text.ParseException {
    LocalDate start = new LocalDate(2001, 4, 13);

    // Every friday the thirteenth.
    String ical = "RRULE:FREQ=MONTHLY"
                  + ";BYDAY=FR"  // every Friday
                  + ";BYMONTHDAY=13"  // that occurs on the 13th of the month
                  + ";COUNT=13";  // stop after 13 occurences

    // Print out each date in the series.
    for (LocalDate date :
         LocalDateIteratorFactory.createLocalDateIterable(ical, start, true)) {
      System.out.println(date);
    }
  }
}

See RFC 2445 for the recurrence rule syntax and what it means, and the examples later in the same document.

If you use java.util.Date and java.util.Calendar in your application instead of Joda-Time, you can use the com.google.ical.compat.javautil package instead to provide Date objects.