Signed v5.1.0 release

Release v5.0.0

Release v4.2.0

Release v4.1.1

Bug: T347759
Change-Id: I60c8ed52b6dd5ac58c1061290dcaa22e86d411f0

Tag 4.1.0 release

* Add add(), sub() methods for date interval arithmetic
* setFakeTime: add $step parameter
* Add microtime() function
* Fix documentation for ConvertibleTimestamp.php

Tagging v4.0.0

Tag 3.0.0 release

* BREAKING CHANGE: the library is now stricter about rejecting some invalid
  formats such as "Wed, 22 May 2019 12:00:00 +1 day" (which is a valid date
  spec in some tools but not in ConvertibleTimestamp which does not accept
  relative date modifiers) or "Wed, 22 May 2019 12:00:00 A potato" (where
  the trailing nonsense got silently ignored before this change).
* Time zones are handled more consistently and more correctly.
* Fix some bugs certain formats had with pre-Unix-epoch dates.
* Relax ISO 8601 syntax: allow space instead of T
* Improve ISO 8601 syntax compliance: accept comma as decimal separator,
  accept non-Z timezones.
* ConvertibleTimestamp::convert can take a DateTime now.

Release v2.2.0

Release 2.1.1

* Updates TS_POSTGRES to match PostgreSQL's actual output format (when
  using datestyle ISO, which is the default).

Introduce a mock clock in ConvertibleTimestamp.

This allows unit tests to force clock behavior.

Bug: T203481
Needed-By: I989e05984b75b2e9c8e07b20eac07e510162bdad
Change-Id: I92eab738f3844772eda033de9b3d9283c82c088a