iCalendar - all appointments at a glance

With iCalendar, you have the opportunity to combine your appointments from different programs into one format. These can then be managed and modified as files in a standardized format. In addition, exchanging info with friends and business partners is much easier: As it uses a global standard, almost anyone can handle the files. Recipients of the ical or ics files have the option to automatically update their calendar with the appointment. This is why iCalendar is an ideal data format for exchanging calendar content for professional and private purposes.

iCalendar: Definition and explanation of the data exchange format

iCalendar is a calendar exchange format for distributing calendar units which is standardized in RFC 5545. This makes it possible to bundle appointments from different applications on your PC and smartphone into a calendar, and to manage and share them from there. The format is based on vCalendar, which was created in 1998. It is possible with the iCal format to practically manage and share all appointments from different calendar functions in real time and in a clear format.


The information within an iCalendar file is not exclusively limited to just dates. To-do lists or meetings can also be organized with the format.

What is ical?

Depending on the operating system, the iCalendar files have a different abbreviation and many people ask, “What is ical, ics or iFBF?” These are file extensions from iCalendar: Although .ics, .ifb, .ical and .ifbf always refer to files in iCal format, they do have some differences.

  • ical: Name extension for macOS
  • ics: Filename extension for all other operating systems
  • ifbf: Contains information about whether you're free or busy (for Mac OS X)
  • ifb: Contains information whether you are free or busy (all other operating systems)

If you want to send an appointment entry, you have to select the file type of the iCalendar format to save and send. The .ics format is often the best choice as it is compatible with most operating systems. When the recipient opens the file, they can decide whether they accept the appointment received or not.


iCalendar files are basically plain text files, which makes sharing among different systems easier

The benefits of iCalendar

iCalendar is not limited to the exchange of files. The format behind the iCalendar appointments is closely linked to the email standard; this is followed by the Multipurpose Internet Mail Extension (MIME) and in particular the type ‘text/calendar’. Thanks to this open design, calendar entries in this format can be placed almost anywhere, and even integrated into web pages. Events can thereby be shared or important appointments published. Together with WebDAV servers which are used to provide files over the Internet, appointments can be synchronized at any time.

Furthermore, the format offers the option of directly exchanging appointments between mobile devices via Bluetooth or a personal network. So, if you want to organize the next appointment in a business meeting, you can simply submit this entry to everyone present. In addition, iCalendar offers the possibility of using all stored information in several applications, which are then synchronized in the format in real time.

The iCalendar format is accepted by popular calendar programs that integrate the web-based data from the calendar:

  • Google Calendar
  • Android Calendar
  • Microsoft Outlook
  • Blackberry Calendar
  • macOS/iOS Calendar

How to create an iCalendar file

From theory to practice. Making an appointment works as follows:

  • First, open a new document in a text editor of your choice. This can also be done on a smartphone with the right app.
  • The file will now be filled with the usual iCalendar pattern, which we will explain in more detail in the next step.
  • After correctly filling out the document, the export takes place in the ical format. For this, the file must be saved with the abbreviation “.ics”.
  • Open a calendar program of your choice and import the ics file as an appointment. Simply click on the corresponding menu item and the appointment will be automatically uploaded from the directory.
  • The appointment can now be found as an entry in your calendar.

In order for the transfer of data to work properly and for the recipient to be able to import the appointment into their ics calendar, you must submit the information in a predefined format. Here, each line has a corresponding meaning:

  • BEGIN:VCALENDAR: This is used to open every iCalendar file.
  • VERSION: The version of the format is indicated here, currently “2.0”.
  • PRODID: The name or the address of the creator or the application used is entered here.
  • METHOD: Indicates how the entry is to be transferred to the recipient. There are two types here: With PUBLISH an entry appears immediately, while REQUEST packages the appointment as a query.
  • BEGIN:VEVENT: This line marks the beginning of the area containing the relevant dates of the appointment.
  • UID: Each ics file, and therefore every calendar entry, requires a unique identifier.
  • LOCATION: At this point the venue is stated, where you can decide yourself how this is done exactly.
  • SUMMARY: This entry gives a short summary of the appointment.
  • DESCRIPTION: Here, a detailed description is given, which can only be seen when the appointment entry is opened.
  • CLASS: It is decided here whether the appointment should be saved publicly (PUBLIC) or privately (PRIVATE).
  • DTSTART: Specifies the start time of the appointment.
  • DTEND: Indicates the end time of the appointment.
  • DTSTAMP: The timestamp contains information on when the calendar entry was created.
  • END:VEVENT: The penultimate row ends the area containing the appointment information.
  • END:VCALENDAR: Completes the file.

The time indication also follows a standardized format:

  • The first four digits correspond to the year (YYYY): 2019
  • The next two, the month (MM): 201910
  • And the last two specify the day (DD): 20191027
  • You can separate the date from the time with the letter T: 20191027T
  • The time, in turn, consists of 6 numbers:
    • Two for the hour: 20191027T15
    • Two for the minute: 20191027T1559
    • And two for the seconds: 20191027T155954
    • The date input is closed with a Z: 20191027T155954Z

In the following example all rows are filled out accordingly.

DESCRIPTION:Kick-off Meeting
DTEND: 20191101T120000Z
DTSTAMP: 20191027T155954Z

Each recipient of the appointment can now have the appointment entered in their calendar by opening the file and thereby receives all relevant information, from the type of appointment to the start and end time, completely automatically. Therefore, the iCalendar format generates real time savings, particularly in professional life.

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