Changes in version 0.1.0.9000                      

New features

  - Added support for multiplication and division of time durations.
  - Added round()/floor()/ceiling() methods for rounding time by
    chronons. (note: use time_round(), time_floor(), and time_ceiling()
    for rounding to a specified time granule).
  - Added casting from time durations to character vectors.
  - Added explicit conversion to naive time by using tz = NA.

Improvements

  - Continuous time model durations now always show at least one decimal
    place.
  - Added formatting support for NaN, Inf, and -Inf values in time
    types.
  - Improved str() output to be more compact for each time type.

Bug fixes

  - Fixed incorrect usage of time_chronon() causing arithmetic to fail.
  - Fixed incompatibilities with vctrs sorting, ptype2, and casting
    methods.
  - Fixed formatting of cyclical time with mixed-calendar chronon and
    cycle (#62).
  - Fixed divmod of Gregorian day -> month and day -> year producing
    incorrect divisors near the year boundary for continuous time dates.

                 Changes in version 0.1.0 (2026-05-19)                  

This is the initial CRAN release of the package with provides the core
data types and temporal manipulation for temporal analysis with mixed
granularity data.

New features

Time

  - The generic mixtime() constructor for creating mixed temporal
    vectors that combine time points of different granularities (e.g.
    monthly and quarterly) in a single vector via vecvec.

Linear time

  - linear_time() creates linear time vectors with a user-specified
    chronon (smallest indivisible time granule), supporting both
    discrete (integer) and continuous (fractional) time models.
  - Convenience functions for common temporal granularities: year(),
    yearquarter(), yearmonth(), yearweek(), date(), and datetime().

Cyclical time

  - cyclical_time() creates cyclical time vectors representing positions
    within a repeating cycle (e.g. day-of-week, month-of-year).
  - Convenience functions for common cyclical temporal granularities:
    month_of_year(), day_of_year(), day_of_month(), day_of_week(),
    week_of_year(), and time_of_day().

Calendar systems

  - Three initial calendar systems:
      - cal_gregorian: standard Gregorian calendar with year, quarter,
        month, day, hour, minute, second, and millisecond units.
      - cal_isoweek: ISO 8601 week-date calendar with ISO year, week,
        and day units. Weeks always start on Monday; the first week of
        the year is the week containing the first Thursday.
      - cal_sym454: Symmetry454 perennial solar calendar with a
        symmetrical 4–5–4 week pattern per quarter and a leap-week rule.

Sequences

  - seq() methods for mixtime and mt_time objects support integer,
    string (e.g. "1 month"), and time unit by arguments, as well as
    length.out and along.with. Overflow behaviour when step granules
    differ from sequence granules can be controlled with on_invalid =
    "nearest" (default) or "overflow".

Rounding

  - round_time(), floor_time(), and ceiling_time() round time objects to
    a specified time granule, preserving the input class and timezone.

Formatting

  - A mixed-calendar general purpose formatting system is provided for
    mixtime objects. The format strings use glue-like {} substitutions
    with the helper functions lin(x) and cyc(x, y) to position linear
    and cyclical time components in a string. x and y are time granules
    from a calendar, which can be used to create general purpose
    mixed-calendar time formats.

Timezone support

  - tz_name() extracts the timezone from a time object.
  - tz_offset() returns the UTC offset for a datetime in its timezone.
  - tz_abbreviation() returns the timezone abbreviation (e.g. "EST",
    "PDT").
  - tz_transitions() returns a data frame of DST and other timezone
    transitions between two time points.

Accessor functions

  - time_calendar() extracts the calendar system from a time object.

tsibble and fable compatibility

  - Methods for tsibble index validation are provided, enabling mixtime
    vectors to be used as time indexes in tsibble objects and in
    forecasting with fable.

Extensibility

  - new_calendar() defines a calendar as a named collection of time unit
    classes, with optional inheritance from another calendar.

  - mt_unit(), mt_tz_unit(), and mt_loc_unit() primitives for creating
    new time units.

  - new_linear_time_fn() and new_cyclical_time_fn() are factories for
    building convenient linear and cyclical time functions (e.g.
    yearmonth()).

  - Calendar arithmetic with:
    
      - chronon_divmod() performs division-with-remainder arithmetic
        between time granules (e.g. 1 day to 1 month), enabling
        cross-granule calendrical arithmetic.
      - chronon_cardinality() returns the number of smaller granules
        contained in a coarser granule (e.g. days in 1 month), with
        context-dependent results for variable-length granules.
      - chronon_epoch() returns the epoch offset for a given time unit.

  - Displaying time with:
    
      - time_unit_abbr() and time_unit_full() for time unit text.
      - linear_labels() and cyclical_labels() for time labels (e.g. Jan,
        Feb, ... for months of year).
      - chronon_format_linear() and chronon_format_cyclical() for
        default formatting strings.
      - chronon_format_attr() for appending attribute information (e.g.
        timezones)

Vignettes

  - Extending mixtime - a vignette on how to define new calendars and
    implement calendar arithmetic for temporal operations within the
    calendar's units and with other calendars.