Casting is one way to change a time point's precision.

Casting to a less precise precision will completely drop information that is more precise than the precision that you are casting to. It does so in a way that makes it round towards zero. When converting time points to a less precise precision, you often want time_point_floor() instead of time_point_cast(), as that handles pre-1970 dates (which are stored as negative durations) in a more intuitive manner.

Casting to a more precise precision is done through a multiplication by a conversion factor between the current precision and the new precision.

time_point_cast(x, precision)



[clock_sys_time / clock_naive_time]

A sys-time or naive-time.



A time point precision. One of:

  • "day"

  • "hour"

  • "minute"

  • "second"

  • "millisecond"

  • "microsecond"

  • "nanosecond"


x cast to the new precision.


# Hour precision time points # One is pre-1970, one is post-1970 x <- duration_hours(c(25, -25)) x <- as_naive_time(x) x
#> <time_point<naive><hour>[2]> #> [1] "1970-01-02 01" "1969-12-30 23"
# Casting rounds the underlying duration towards 0 cast <- time_point_cast(x, "day") cast
#> <time_point<naive><day>[2]> #> [1] "1970-01-02" "1969-12-31"
# Flooring rounds the underlying duration towards negative infinity, # which is often more intuitive for time points. # Note that the cast ends up rounding the pre-1970 date up to the next # day, while the post-1970 date is rounded down. floor <- time_point_floor(x, "day") floor
#> <time_point<naive><day>[2]> #> [1] "1970-01-02" "1969-12-30"
# Casting to a more precise precision, hour->millisecond time_point_cast(x, "millisecond")
#> <time_point<naive><millisecond>[2]> #> [1] "1970-01-02 01:00:00.000" "1969-12-30 23:00:00.000"