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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.

Usage

time_point_cast(x, precision)

Arguments

x

[clock_sys_time / clock_naive_time]

A sys-time or naive-time.

precision

[character(1)]

A time point precision. One of:

  • "day"

  • "hour"

  • "minute"

  • "second"

  • "millisecond"

  • "microsecond"

  • "nanosecond"

Value

x cast to the new precision.

Examples

# 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] "1970-01-02T01" "1969-12-30T23"

# 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] "1970-01-02T01:00:00.000" "1969-12-30T23:00:00.000"