4.0.0-beta1

• #258: Support for expanding events that use RDATE. (@jabdoa2)
• #258: Correctly support TZID for events that use RDATE. (@jabdoa2)
• #240: Component\VCalendar::expand() now returns a new expanded VCalendar
  object, instead of editing the existing VCalendar in-place. This is a BC
  break.
• #265: Using the new InvalidDataException in place of
  InvalidArgumentException and LogicException in all places where we fail
  because there was something wrong with input data.
• #227: Always add VALUE=URI to PHOTO properties.
• #235: Always add VALUE=URI to URL properties.
• It's now possible to override which class is used instead of
  Component\VCalendar or Component\VCard during parsing.
• #263: Lots of small cleanups. (@jakobsack)
• #220: Automatically stop recurring after 3500 recurrences.
• #41: Allow user to set different encoding than UTF-8 when decoding vCards.
• #41: Support the ENCODING parameter from vCard 2.1.
  Both ISO-8859-1 and Windows-1252 are currently supported.
• #185: Fix encoding/decoding of TIME values in jCal/jCard.

4.0.0-alpha2

• Updated windows timezone file to support new mexican timezone.
• #239: Added a BirthdayCalendarGenerator. (@DominikTo)
• #250: isInTimeRange() now considers the timezone for floating dates and
  times. (@armin-hackmann)
• Added a duplicate vcard merging tool for the command line.
• #253: isInTimeRange() now correctly handles events that throw the
  NoInstancesException exception. (@migrax, @DominikTo)
• #254: The parser threw an E_NOTICE for certain invalid objects. It now
  correctly throws a ParseException.

3.4.7

• Handle isInTimeRange for recurring events that have 0 valid instances. (@DominikTo, @migrax).

3.4.6

• #250: recurring all-day events are incorrectly included in time range
  requests when not using utc in the time range. (@armin-hackmann)

4.0.0-alpha1

• sabre/vobject now requires PHP 5.5.
• #244: PHP7 support.
• Lots of speedups and reduced memory usage!
• #160: Support for xCal a.k.a. RFC6321! (@Hywan)
• #192: Support for xCard a.k.a. RFC6351! (@Hywan)
• #139: We now accept DateTimeInterface wherever it accepted DateTime
  before in arguments. This means that either DateTime or
  DateTimeImmutable may be used everywhere.
• #242: Full support for the VAVAILABILITY component, and calculating
  VFREEBUSY based on VAVAILABILITY data.
• #186: Fixing conversion of UTC-OFFSET properties when going back and
  forward between jCal and iCalendar.
• Properties, Components and Parameters now implement PHP's JsonSerializable
  interface.
• #139: We now always return DateTimeImmutable from any method. This could
  potentially have big implications if you manipulate Date objects anywhere.
• #161: Simplified ElementList by extending ArrayIterator.
• Removed RecurrenceIterator (use Recur\EventIterator instead).
• Now using php-cs-fixer to automatically enforce and correct CS.
• #233: The +00:00 timezone is now recognized as UTC. (@c960657)
• #237: Added a destroy() method to all documents. This method breaks any
  circular references, allowing PHP to free up memory.
• #197: Made accessing properties and objects by their name a lot faster. This
  especially helps objects that have a lot of sub-components or properties,
  such as large iCalendar objects.
• #197: The $children property on components has been changed from public
  to protected. Use the children() method instead to get a flat list of
  objects.
• #244: The Float and Integer classes have been renamed to FloatValue
  and IntegerValue to allow PHP 7 compatibility.

3.4.5

• #229: Converting vcards from 3.0 to 4.0 that contained a LANG property
  would throw an error.

3.4.4

• #228: Fixed a 'party crasher' bug in the iTip broker. This would break
  scheduling in some cases.

3.4.3

• #219: Corrected validation of EXDATE properties with more than one value.
• #212: BYSETPOS with values below -1 was broken and could cause infinite
  loops.
• #211: Fix BYDAY=-5TH in recurrence iterator. (@lindquist)
• #216: ENCODING parameter is now validated for all document types.
• #217: Initializing vCard DATE objects with a PHP DateTime object will now
  work correctly. (@thomascube)

3.4.2

• #210: iTip: Replying to an event without a master event was broken.

3.4.1

• A minor change to ensure that unittests work correctly in the sabre/dav
  test-suite.