As @andresrcs noted, we really need a small reproducible example (aka a self-contained reprex ) to be sure, as it depends on how the times are stored in your file.
If they're strings, you might want to look at the hms package (part of the tidyverse, but not attached by default).
library(tidyverse)
dat <- tibble::tribble(
~record, ~time,
"a", "12:30",
"b", "1:45",
"c", "2:30"
)
dat
#> # A tibble: 3 x 2
#> record time
#> <chr> <chr>
#> 1 a 12:30
#> 2 b 1:45
#> 3 c 2:30
dat %>%
mutate(time = hms::parse_hm(time))
#> # A tibble: 3 x 2
#> record time
#> <chr> <time>
#> 1 a 12:30
#> 2 b 01:45
#> 3 c 02:30
Created on 2018-11-30 by the reprex package (v0.2.1.9000)
See also several suggestions here:
For pointers on making a reprex, check out the reprex FAQ
Here's an example using a csv with similar data that I put into a gist:
library(readr)
dummy <- read_csv("https://gist.githubusercontent.com/batpigandme/868fcf6cfb3a0accf1ad6a7d0b52f4e7/raw/c3232afd7cb4c1d3b39022a230d4b23b5cbb9c6b/demo_csv.csv",
col_types = cols(time = col_time(format = "%H:%M")))
dummy
#> # A tibble: 3 x 2
#> record time
#> <chr> <time>
#> 1 a 12:30
#> 2 b 01:45
#> 3 c 02:15
Created on 2018-11-30 by the reprex package (v0.2.1.9000)