NAs                     The 'datey', 'durationy' and 'datey_interval'
                        versions of NA
all_of_time             'All of time' — the maximum valid
                        'datey_interval'
as_years_datey          Convert a 'datey' to calendar years (including
                        fractional part)
as_years_durationy      Convert a 'durationy' to duration in years
combine                 Combine multiple 'datey', 'durationy' or
                        'datey_interval' vectors
datey                   Create a 'datey'
datey_components        Get year, month, day or day_fraction breakdown
                        of a 'datey'
datey_interval          Create a 'datey_interval'
durationy               Create a 'durationy' from an annual duration
integer_constants       Integer constants
interval_includes       Whether a 'datey_interval' includes a 'datey'
interval_nature         Properties of a 'datey_interval'
interval_properties     Get the start, end or duration of a
                        'datey_interval'
is_NA                   Whether 'datey', 'durationy' or
                        'datey_interval' are NA
is_leap_year            Is 'x' a leap year?
is_type                 Is 'x' a 'datey', 'durationy' or
                        'datey_interval'?
is_xxx_day              Is a 'datey' the start (or end) or middle of a
                        day?
max_min                 Minimum, maximum or range of 'datey' or
                        'durationy'
mean                    Mean value of 'datey' or 'durationy'
ops                     Operators for 'datey', 'durationy' and
                        'datey_interval'
seq                     Create 'datey' or 'durationy' sequence vector
subset                  Subset 'datey', 'durationy' or 'datey_interval'
                        vectors
text_from_datey         Format or print a 'datey'
text_from_datey_interval
                        Format or print a 'datey_interval'
text_from_durationy     Format or print a 'durationy'
