trunc.POSIXt: Return the floor, ceiling, or rounded value of date or time to
specified unit.
Description
truncPOSIXt returns the date truncated to the specified unit.
ceil.POSIXt returns next ceiling of the date at the unit selected in
units.
roundPOSIXt returns the date or time value rounded to nearest
specified unit selected in digits.
truncPOSIXt and roundPOSIXt have been extended from
the base package functions trunc.POSIXt and
round.POSIXt which in the future will add the other time units
we need.