Inspects a data frame's time column and returns its type.
Examples
# "numeric"
casteval:::get_time_type(data.frame(time=c(1,2,3)))
#> [1] "numeric"
# "date"
casteval:::get_time_type(data.frame(time=lubridate::as_date(1:3)))
#> [1] "date"
# "date-time"
casteval:::get_time_type(data.frame(time=lubridate::ymd_hms("2024-01-01_12:34:56")))
#> [1] "date-time"
# unsupported type
try(casteval:::get_time_type(list("January 1", "January 2")))
#> Error in casteval:::get_time_type(list("January 1", "January 2")) :
#> data frame does not contain time column