# era 0.6.0

* `yr_earlier_than()`, `yr_later_than()`, `yr_not_earlier_than()`, and `yr_not_later_than()` implement chronological comparison of year vectors
* `yr_difference()` implements chronological difference of year vectors
* Added `CITATION.cff` file with software citation metadata (#49)

# era 0.5.0

* New `yr_sort()` function for chronological ordering of year vectors (#44)
* New `yr_earliest()`, `yr_latest()`, and `yr_range()` functions for chronological extremes of year vectors (#43)

# era 0.4.1

This patch fixes a malfunctioning test that was causing CRAN checks to fail. There are no significant changes.

* Fixed malfunctioning check

# era 0.4.0

* New eras:
  * Anno Mundi (Hebrew calendar)
* New year units:
  * Sidereal, tropical, and anomalistic astronomic years #15
  * Hebrew lunisolar years
* Changes to existing eras:
  * More precise epoch value for Hijri eras: `621.5394` instead of `622`.
  * More precise epoch value for Nowruz (Solar Hijri) eras: `621.2218` instead of `622`.
* Fixed recurring issues related to the absence of a year 0 in BCE/CE #4
* `this_year()` now considers the current date, returns a floored integer (i.e. the actual current calendar year), and is vectorised over `era`.
* Added pillar printing methods for `era` (#33) and `era_year` (#34) in tibbles
* Class constructors `era()` and `yr()` now return a zero-length vector when called with no arguments (instead of an error), allowing them to be used as [prototypes](https://vctrs.r-lib.org/articles/type-size.html)
* `era_yr` objects can now be cast to character vectors (e.g. `as.character(yr(1, "BP"))`)
* Combining otherwise equivalent eras with different names or labels with `c()` now triggers a warning (#27), consistent with combining them using arithmetic (#3)
* The `era` package no longer exports `magrittr`'s pipe operator (`%>%`)

# era 0.3.1

CRAN release.

* Fixed moved link in README

# era 0.3.0

Second beta / CRAN pre-release.

* Added new era definitions:
  * Islamic calendars (Lunar Hijri, Solar Hijri).
  * Julian calendar
* Reworked era definition scheme:
  * Unit is now represented by the `era_year` class, which describes its length in solar days as well as its name. Added functions for constructing and working with `era_year` objects: `era_year()`, `is_era_year()`, `era_year_label()`, `era_year_days()`.
  * Direction is now coded as `1` ("forwards") or `-1` ("backwards"). The previous character arguments still work but are deprecated.
  * Equality tests for eras now only check significant parameters (i.e. not "label" or "name"), allowing for coercion between functionally equivalent eras, e.g. `yr(1, "BP") + yr(1, "cal BP")` now works (with a warning) (#3).
* Improved `yr_transform()`:
  * Can now convert between eras with different year units (#25).
  * Now has a `precision` argument, allowing the result to be rounded (#23).
* `era` and `yr` objects are now validated when constructed, using new functions `validate_era()`/`is_valid_era()` and `validate_yr()`/`is_valid_yr()` (#7 and #8).
* Minor changes/bug fixes:
  * Added `this_year()`, which returns the current year as a `yr` object.
  * `era(NA)` now returns an error, not a vector of all standard eras (#20).
  * All `era` arguments in functions can now accept a character vector (#20)
  * `era(<era>)` now returns an era with the same parameters (to enable the above)
  * Various additions to make the [coercion hierarchy](https://vctrs.r-lib.org/reference/theory-faq-coercion.html) for era_yrs more consistent; most notably, the common prototype of era_yr, integer, and double, is now era_yr.
  * Fixed printing of NA eras (#9)
  * Errors now use the rlang format and are in general more informative (#26 and #28)

# era 0.2.0

First beta release, including:

* S3 vector class `yr` (`era_yr`) representing years with an era
  * `yr()` constructor
  * Functions for getting and setting the era of a `yr` object: `yr_era()`, `yr_era()<-` and `yr_set_era()`
  * Format and print methods for `yr`s
  * Vector arithmetic methods for `yr`s
* S3 record class `era` representing an era definition
  * `era()` constructor
  * Format and print methods for `era`s
  * Getter functions for era parameters: `era_label()`, `era_name()`, `era_epoch()`, `era_unit()`, `era_scale()`, `era_direction()`
  * `eras()` defining standard eras
* `yr_transform()` function for converting years between eras
* Function documentation and introductory vignette: `vignette("era")`
* A `NEWS.md` file to track changes to the package.

# era 0.1.0

Initial development version.
