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Introduction

iCalendar is a standard method of transferring calendar information between computer systems. The standard allows products from many vendors to transfer calendar information between each other.  iCalendar files typically have the file extension ".ical" ".ics" ".ifb"  or ".icalendar" with a MIME type of "text/calendar".

The iCalendar open standard should not be confused with iCal, the former name for the commercial product "Calendar" developed by Apple Computer.

History

iCalendar was first defined as a standard as RFC 2445 in 1998 by the Internet Engineering Task Force (IETF). This document was authored by Frank Dawson of Lotus Notes Corporation (now owned by IBM) and Derik Stenerson of Microsoft Corporation. The pairing of these two individuals from competing software companies highlighted the need at that time for companies to work together to provide interoperability standards between calendar products.  This interoperability continues to the present day extending support to new technologies such as web site calendar services, smart phones and tablets.

The iCalendar standard was refined in 2009 as RFC 5545 and edited by Bernard Desruisseaux of Oracle Corporation. This resolved some ambiguities from the original standard as well as deprecated a few features that were no longer needed. RFC 5545 is now considered the iCalendar standard and supersedes the previous RFC. RFC 7986 was published in 2016 and adds to the original iCalendar RFC by defining new properties to support conferencing systems and to the main VCALENDAR object including a calendar name, description and refresh interval.

Today, iCalendar is used to import and synchronize events on various platforms, including smart phones, computer and web applications.  Web applications include Microsoft Office 365, Apple Calendar, Google Calendar, and Yahoo Calendar.

iCalendar File Format

Here is a sample iCalendar file containing a single event.

BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//ZContent.net//Zap Calendar 1.0//EN
CALSCALE:GREGORIAN
METHOD:PUBLISH
BEGIN:VEVENT
SUMMARY:Abraham Lincoln
UID:c7614cff-3549-4a00-9152-d25cc1fe077d
SEQUENCE:0
STATUS:CONFIRMED
TRANSP:TRANSPARENT
RRULE:FREQ=YEARLY;INTERVAL=1;BYMONTH=2;BYMONTHDAY=12
DTSTART:20080212
DTEND:20080213
DTSTAMP:20150421T141403
CATEGORIES:U.S. Presidents,Civil War People
LOCATION:Hodgenville\, Kentucky
GEO:37.5739497;-85.7399606
DESCRIPTION:Born February 12\, 1809\nSixteenth President (1861-1865)\n\n\n
 \nhttp://AmericanHistoryCalendar.com
URL:http://americanhistorycalendar.com/peoplecalendar/1,328-abraham-lincol
 n
END:VEVENT
END:VCALENDAR

An iCalendar file consists of sections starting with "BEGIN:" and ending with "END:".  The "VCALENDAR" is the global section that holds all other sections.  Other sections include "VEVENT" for events, "VTODO" for to-do items, "VJOURNAL" for journal entries, and "VTIMEZONE" for time zone information.  Multiple sections of the same type can be repeated.  For example, multiple "VEVENT" sections can occur in an iCalendar file to describe multiple events.

CalDAV: Remote Event Management

The WebDAV standard enables editing web sites remotely.  This standard has been extended to create the CalDAV standard.  Similar to the WebDAV standard, CalDAV enables the management of events from a remote location.  Calendar clients such as Mozilla's Sunbird and Apple's Calendar applications allow editing of events that reside on a remote server.  

Extending the iCalendar Standard

Although the iCalendar specification is very detailed and covers many aspects of calendaring and scheduling, users have found some features lacking in the standard.  Fortunately, the standard is extensible and provides a method of adding additional information to an iCalendar data stream.  Since these features are not part of the standard, support for them will vary from vendor to vendor. A few of these extensions are listed here.

HTML In Event Descriptions

The original iCalendar standard allowed only plain text as part of an event description.  HTML markup, such as font attributes (bold, underline) and layout (div, table) was not allowed in the text description field.  First seen in Microsoft Outlook, the X-ALT-DESC parameter provides a method to add HTML to an event description.  "X-" fields are allowed for non-standard, experimental parameters. This field has become the method of choice when including HTML in a description.  When using HTML, both fields must be included so that iCalendar readers that do not support the X-ALT-DESC field can still read the text version.

Detailed Location/Venue Information

The original iCalendar standard provided a single element for a location description.  This proved inadequate for some who wanted to include additional information about the location, including address, contact information and a description of the location.  A draft proposal entitled, "Internet Calendaring and Scheduling Venue Component Specification" was published in 2007 by Charles Norris of Eventful.com and Jeff McCullough of the University of California, Berkley, to address these issues.  Although it was never fully adopted as an RFC, this document provides a standard method for transferring venue information where the iCalendar standard is lacking.

 

Privacy Policy

Our Privacy Policy was last updated on December 13, 2023.

This Privacy Policy describes Our policies and procedures on the collection, use and disclosure of Your information when You use the Service and tells You about Your privacy rights and how the law protects You.

We use Your Personal data to provide and improve the Service. By using the Service, You agree to the collection and use of information in accordance with this Privacy Policy. This Privacy Policy was generated by TermsFeed Google Analytics Privacy Policy Template.

Interpretation and Definitions

Interpretation

The words of which the initial letter is capitalized have meanings defined under the following conditions. The following definitions shall have the same meaning regardless of whether they appear in singular or in plural.

Definitions

For the purposes of this Privacy Policy:

• "Account" means a unique account created for You to access our Service or parts of our Service.

• "Company" (referred to as either "the Company", "We", "Us" or "Our" in this Agreement) refers to "iCalendar.org"

• "Country" refers to "United States".

• "Cookies" are small files that are placed on Your computer, mobile device or any other device by a website, containing the details of Your browsing history on that website among its many uses.

• "Device" means any device that can access the Service such as a computer, a cellphone or a digital tablet.

• "Personal Data" is any information that relates to an identified or identifiable individual.

• "Service" refers to the Website.

• "Usage Data" refers to data collected automatically, either generated by the use of the Service or from the Service infrastructure itself (for example, the duration of a page visit).

• "Website" refers to "iCalendar.org, accessible from "https://icalendar.org"

• "You" means the individual accessing or using the Service, or the company, or other legal entity on behalf of which such individual is accessing or using the Service, as applicable.

Collecting and Using Your Personal Data

Types of Data Collected

Usage Data

Usage Data is collected automatically when using the Service.

Usage Data may include information such as Your Device's Internet Protocol address (e.g. IP address), browser type, browser version, the pages of our Service that You visit, the time and date of Your visit, the time spent on those pages, unique device identifiers and other diagnostic data.

When You access the Service by or through a mobile device, We may collect certain information automatically, including, but not limited to, the type of mobile device You use, Your mobile device unique ID, the IP address of Your mobile device, Your mobile operating system, the type of mobile Internet browser You use, unique device identifiers and other diagnostic data.

We may also collect information that Your browser sends whenever You visit our Service or when You access the Service by or through a mobile device.

Tracking Technologies and Cookies

We use Cookies and similar tracking technologies to track the activity on Our Service and store certain information. Tracking technologies used are beacons, tags, and scripts to collect and track information and to improve and analyze Our Service. The technologies We use may include:

• Cookies or Browser Cookies. A cookie is a small file placed on Your Device. You can instruct Your browser to refuse all Cookies or to indicate when a Cookie is being sent. However, if You do not accept Cookies, You may not be able to use some parts of our Service. Unless you have adjusted Your browser setting so that it will refuse Cookies, our Service may use Cookies.
• Web Beacons. Certain sections of our Service and our emails may contain small electronic files known as web beacons (also referred to as clear gifs, pixel tags, and single-pixel gifs) that permit the Company, for example, to count users who have visited those pages or opened an email and for other related website statistics (for example, recording the popularity of a certain section and verifying system and server integrity).

Cookies can be "Persistent" or "Session" Cookies. Persistent Cookies remain on Your personal computer or mobile device when You go offline, while Session Cookies are deleted as soon as You close Your web browser.

We use both Session and Persistent Cookies for the purposes set out below:

• Necessary / Essential Cookies

  Type: Session Cookies

  Administered by: Us

  Purpose: These Cookies are essential to provide You with services available through the Website and to enable You to use some of its features. They help to authenticate users and prevent fraudulent use of user accounts. Without these Cookies, the services that You have asked for cannot be provided, and We only use these Cookies to provide You with those services.

• Cookies Policy / Notice Acceptance Cookies

  Type: Persistent Cookies

  Administered by: Us

  Purpose: These Cookies identify if users have accepted the use of cookies on the Website.

• Functionality Cookies

  Type: Persistent Cookies

  Administered by: Us

  Purpose: These Cookies allow us to remember choices You make when You use the Website, such as remembering your login details or language preference. The purpose of these Cookies is to provide You with a more personal experience and to avoid You having to re-enter your preferences every time You use the Website.

• Tracking and Performance Cookies

  Type: Persistent Cookies

  Administered by: Third-Parties

  Purpose: These Cookies are used to track information about traffic to the Website and how users use the Website. The information gathered via these Cookies may directly or indirectly identify you as an individual visitor. This is because the information collected is typically linked to a pseudonymous identifier associated with the device you use to access the Website. We may also use these Cookies to test new pages, features or new functionality of the Website to see how our users react to them.

For more information about the cookies we use and your choices regarding cookies, please visit our Cookies Policy or the Cookies section of our Privacy Policy.

Use of Your Personal Data

The Company may use Personal Data for the following purposes:

• To provide and maintain our Service, including to monitor the usage of our Service.

• To manage Your Account: to manage Your registration as a user of the Service. The Personal Data You provide can give You access to different functionalities of the Service that are available to You as a registered user.

• For the performance of a contract: the development, compliance and undertaking of the purchase contract for the products, items or services You have purchased or of any other contract with Us through the Service.

• To contact You: To contact You by email, telephone calls, SMS, or other equivalent forms of electronic communication, such as a mobile application's push notifications regarding updates or informative communications related to the functionalities, products or contracted services, including the security updates, when necessary or reasonable for their implementation.

• To provide You with news, special offers and general information about other goods, services and events which we offer that are similar to those that you have already purchased or enquired about unless You have opted not to receive such information.

• To manage Your requests: To attend and manage Your requests to Us.

• For business transfers: We may use Your information to evaluate or conduct a merger, divestiture, restructuring, reorganization, dissolution, or other sale or transfer of some or all of Our assets, whether as a going concern or as part of bankruptcy, liquidation, or similar proceeding, in which Personal Data held by Us about our Service users is among the assets transferred.

• For other purposes: We may use Your information for other purposes, such as data analysis, identifying usage trends, determining the effectiveness of our promotional campaigns and to evaluate and improve our Service, products, services, marketing and your experience.

We may share Your personal information in the following situations:

• With Service Providers: We may share Your personal information with Service Providers to monitor and analyze the use of our Service, for payment processing, to contact You.
• For business transfers: We may share or transfer Your personal information in connection with, or during negotiations of, any merger, sale of Company assets, financing, or acquisition of all or a portion of Our business to another company.
• With Affiliates: We may share Your information with Our affiliates, in which case we will require those affiliates to honor this Privacy Policy. Affiliates include Our parent company and any other subsidiaries, joint venture partners or other companies that We control or that are under common control with Us.
• With business partners: We may share Your information with Our business partners to offer You certain products, services or promotions.
• With other users: when You share personal information or otherwise interact in the public areas with other users, such information may be viewed by all users and may be publicly distributed outside.
• With Your consent: We may disclose Your personal information for any other purpose with Your consent.

Retention of Your Personal Data

The Company will retain Your Personal Data only for as long as is necessary for the purposes set out in this Privacy Policy. We will retain and use Your Personal Data to the extent necessary to comply with our legal obligations (for example, if we are required to retain your data to comply with applicable laws), resolve disputes, and enforce our legal agreements and policies.

The Company will also retain Usage Data for internal analysis purposes. Usage Data is generally retained for a shorter period of time, except when this data is used to strengthen the security or to improve the functionality of Our Service, or We are legally obligated to retain this data for longer time periods.

Transfer of Your Personal Data

Your information, including Personal Data, is processed at the Company's operating offices and in any other places where the parties involved in the processing are located. It means that this information may be transferred to — and maintained on — computers located outside of Your state, province, country or other governmental jurisdiction where the data protection laws may differ than those from Your jurisdiction.

Your consent to this Privacy Policy followed by Your submission of such information represents Your agreement to that transfer.

The Company will take all steps reasonably necessary to ensure that Your data is treated securely and in accordance with this Privacy Policy and no transfer of Your Personal Data will take place to an organization or a country unless there are adequate controls in place including the security of Your data and other personal information.

Disclosure of Your Personal Data

Business Transactions

If the Company is involved in a merger, acquisition or asset sale, Your Personal Data may be transferred. We will provide notice before Your Personal Data is transferred and becomes subject to a different Privacy Policy.

Law enforcement

Under certain circumstances, the Company may be required to disclose Your Personal Data if required to do so by law or in response to valid requests by public authorities (e.g. a court or a government agency).

Other legal requirements

The Company may disclose Your Personal Data in the good faith belief that such action is necessary to:

• Comply with a legal obligation
• Protect and defend the rights or property of the Company
• Prevent or investigate possible wrongdoing in connection with the Service
• Protect the personal safety of Users of the Service or the public
• Protect against legal liability

Security of Your Personal Data

The security of Your Personal Data is important to Us, but remember that no method of transmission over the Internet, or method of electronic storage is 100% secure. While We strive to use commercially acceptable means to protect Your Personal Data, We cannot guarantee its absolute security.

Detailed Information on the Processing of Your Personal Data

The Service Providers We use may have access to Your Personal Data. These third-party vendors collect, store, use, process and transfer information about Your activity on Our Service in accordance with their Privacy Policies.

Analytics

We may use third-party Service providers to monitor and analyze the use of our Service.

• Google Analytics

  Google Analytics is a web analytics service offered by Google that tracks and reports website traffic. Google uses the data collected to track and monitor the use of our Service. This data is shared with other Google services. Google may use the collected data to contextualize and personalize the ads of its own advertising network.

  You can opt-out of having made your activity on the Service available to Google Analytics by installing the Google Analytics opt-out browser add-on. The add-on prevents the Google Analytics JavaScript (ga.js, analytics.js and dc.js) from sharing information with Google Analytics about visits activity.

  For more information on the privacy practices of Google, please visit the Google Privacy & Terms web page: https://policies.google.com/privacy

Children's Privacy

Our Service does not address anyone under the age of 13. We do not knowingly collect personally identifiable information from anyone under the age of 13. If You are a parent or guardian and You are aware that Your child has provided Us with Personal Data, please contact Us. If We become aware that We have collected Personal Data from anyone under the age of 13 without verification of parental consent, We take steps to remove that information from Our servers.

If We need to rely on consent as a legal basis for processing Your information and Your country requires consent from a parent, We may require Your parent's consent before We collect and use that information.

Your California Privacy Rights (California's Shine the Light law)

Under California Civil Code Section 1798 (California's Shine the Light law), California residents with an established business relationship with us can request information once a year about sharing their Personal Data with third parties for the third parties' direct marketing purposes.

If you'd like to request more information under the California Shine the Light law, and if You are a California resident, You can contact Us using the contact information provided below.

California Privacy Rights for Minor Users (California Business and Professions Code Section 22581)

California Business and Professions Code Section 22581 allows California residents under the age of 18 who are registered users of online sites, services or applications to request and obtain removal of content or information they have publicly posted.

To request removal of such data, and if You are a California resident, You can contact Us using the contact information provided below, and include the email address associated with Your account.

Be aware that Your request does not guarantee complete or comprehensive removal of content or information posted online and that the law may not permit or require removal in certain circumstances.

Links to Other Websites

Our Service may contain links to other websites that are not operated by Us. If You click on a third party link, You will be directed to that third party's site. We strongly advise You to review the Privacy Policy of every site You visit.

We have no control over and assume no responsibility for the content, privacy policies or practices of any third party sites or services.

Changes to this Privacy Policy

We may update Our Privacy Policy from time to time. We will notify You of any changes by posting the new Privacy Policy on this page.

We will let You know via email and/or a prominent notice on Our Service, prior to the change becoming effective and update the "Last updated" date at the top of this Privacy Policy.

You are advised to review this Privacy Policy periodically for any changes. Changes to this Privacy Policy are effective when they are posted on this page.

Contact Us

If you have any questions about this Privacy Policy, You can contact us:

• By visiting this page on our website: https://icalendar.org/contact-us.html

 

The Zap Cal Library is an open source PHP library for reading and writing iCalendar files.  The library has been in development for over 10 years supporting the Zap Calendar program, an open source application for the Joomla CMS, and more recently the iCalendar validator project at iCalendar.org.  It is now available as a standalone library for PHP developers.

The library can be downloaded at GitHub at https://github.com/zcontent/icalendar

The API documentation can be found at http://iCalendar.org/zapcallibdocs

The Zap Calendar iCalendar Library is a PHP library for supporting the iCalendar (RFC 5545) standard. Several examples of reading and writing iCalendar files are included in the library

This PHP library is for reading and writing iCalendar formatted feeds and files. Features of the library include:

• Read AND write support for iCalendar files
• Object based creation and manipulation of iCalendar files
• Supports expansion of RRULE to a list of repeating dates
• Supports adding timezone info to iCalendar file

All iCalendar data is stored in a PHP object tree. This allows any property to be added to the iCalendar feed without requiring specialized library function calls. With power comes responsibility. Missing or invalid properties can cause the resulting iCalendar file to be invalid. Visit iCalendar.org to view valid properties and test your feed using the site's iCalendar validator tool.

Here is an example of a PHP program to create a single event iCalendar file:

 

<?php
$title = "Simple Event";
// date/time is in SQL datetime format
$event_start = "2020-01-01 12:00:00";
$event_end = "2020-01-01 13:00:00";

// create the ical object
$icalobj = new ZCiCal();

// create the event within the ical object
$eventobj = new ZCiCalNode("VEVENT", $icalobj->curnode);

// add title
$eventobj->addNode(new ZCiCalDataNode("SUMMARY:" . $title));

// add start date
$eventobj->addNode(new ZCiCalDataNode("DTSTART:" . ZCiCal::fromSqlDateTime($event_start)));

// add end date
$eventobj->addNode(new ZCiCalDataNode("DTEND:" . ZCiCal::fromSqlDateTime($event_end)));

// UID is a required item in VEVENT, create unique string for this event
// Adding your domain to the end is a good way of creating uniqueness
$uid = date('Y-m-d-H-i-s') . "@demo.icalendar.org";
$eventobj->addNode(new ZCiCalDataNode("UID:" . $uid));

// DTSTAMP is a required item in VEVENT
$eventobj->addNode(new ZCiCalDataNode("DTSTAMP:" . ZCiCal::fromSqlDateTime()));

// Add description
$eventobj->addNode(new ZCiCalDataNode("Description:" . ZCiCal::formatContent(
        "This is a simple event, using the Zap Calendar PHP library. " .
        "Visit http://icalendar.org to validate icalendar files.")));

// write iCalendar feed to stdout
echo $icalobj->export();