a string, Period
object or a date-time object. When a singleton string,
it specifies a time unit or a multiple of a unit to be rounded to. Valid base units
are second
, minute
, hour
, day
, week
, month
, bimonth
, quarter
,
season
, halfyear
and year
. Arbitrary unique English abbreviations as in the
period()
constructor are allowed. Rounding to multiples of units (except weeks)
is supported. When unit
is a Period
object, units of the period objects are
used. This is equivalent to converting the period object to its string
representation and passing as unit
argument.
When unit
is a date-time object rounding is done to the nearest of the
elements in unit
. If range of unit
vector does not cover the range of
x
ceiling_date()
and floor_date()
round to the max(x)
and min(x)
for elements that fall outside of range(unit)
.