clock 0.7.0

New features

• New year_week_day() calendar for specifying a date using the year, the week
  number, and the day of the week, alongside a start value representing the
  day of the week that is considered the start of the week. Using
  start = clock_weekdays$monday is identical to the iso_year_week_day()
  calendar, and using start = clock_weekdays$sunday is useful for representing
  the Epidemiological calendar used by the US CDC guidelines (similar to what
  is supported by lubridate::epiweek() and lubridate::epiyear()) (#110).

• New date_spanning_seq() for generating a regular sequence along the full
  span of a date or date-time vector (i.e. along [min(x), max(x)]). It is
  similar to tidyr::full_seq(), but is a bit simpler and currently has better
  handling of some edge cases. Additionally included in the low-level API are
  calendar_spanning_seq(), time_point_spanning_seq(), and
  duration_spanning_seq() (#279).

• New date_time_info() and zoned_time_info() low-level helpers for accessing
  the previous/next transition times, the offset from UTC, and the current time
  zone abbreviation (#295).

• calendar_leap_year() now supports the year-quarter-day and iso-year-week-day
  calendars (#332, #333).

Breaking changes

• The storage mechanism for the duration, sys-time, naive-time, and zoned-time
  types has been altered to more correctly represent the full range of values
  allowed by the underlying C++ types. This means that if you have serialized
  a value of one of these types with an old version of clock, then it will no
  longer unserialize correctly going forward.

  Technically, rather than storing a variable number of integer vectors
  representing ticks, ticks of a day, and ticks of a second, we now always store
  values of these types within two double vectors, regardless of the precision.
  This simplifies the implementation and allows us to represent the full range
  of possible int64_t values (#331).

Lifecycle changes

• date_zone() and date_set_zone() have been soft-deprecated in favor of
  date_time_zone() and date_time_set_zone() (#326).

Minor changes and bug fixes

• clock now compiles significantly faster (on a 2018 Intel Mac, it used to take
  ~70 seconds for a full compilation, and now takes ~25 seconds) (#322).

• %% and %/% operators now return a missing value when the right-hand side
  is 0. For %/%, this is consistent with 2L %/% 0L, which returns a
  missing value, rather than with 2 %/% 0, which returns Inf, since
  infinite durations are not supported (#349).

• seq() methods for durations and time points handle the empty sequence cases
  of from > to && by > 0 and from < to && by < 0 better when from and to
  are very far apart (i.e. when they would otherwise result in overflow if they
  were subtracted).

• zoned_time_zone() and zoned_time_set_zone() are no longer generic, and now
  only work for zoned-times.

• Documented clock's current stance on leap seconds in the FAQ vignette (clock
  ignores them like POSIXct) (#309).

• Duration vectors now work as .before and .after arguments of
  slider::slide_index() and friends (#306).

• All as_*() generics exported by clock now include ... in their signature
  to help with extensibility of converting to clock types. These are the only
  clock generics that are currently "blessed" as fully extensible (#348).

• as.character() has been implemented for durations.

• Fixed vec_ptype_full() and vec_ptype_abbr() methods for sys-time and
  naive-time objects (#302).

• Many errors have been improved (#219, #286, #595).

• Renamed locale.h to fill.h to avoid clock's locale.h being chosen over a
  system header of the same name on some CentOS machines (#310).

• Skipped a test on 32-bit architectures to work around a bug in base R (#312).

• R >=3.5.0 is now required, which is in line with tidyverse standards.

• vctrs >=0.6.1 and rlang >=1.1.0 are now required.