You can use tidyr::separate()
see this example
library(tidyverse)
sample_df <- data.frame(
date = c("2015-01-01 08:10:00 AM")
)
sample_df %>%
separate(date, into = c("year", "month", "day", "hour"), extra = "drop")
#> year month day hour
#> 1 2015 01 01 08
Created on 2020-04-29 by the reprex package (v0.3.0)
If you need more specific help, please provide a proper REPRoducible EXample (reprex) illustrating your issue.