В lubridate
мы можем использовать parse_date_time
lubridate::parse_date_time(df$V1, "IMp mdy")
#Seems to work fine with "H" as well instead of "I"
#lubridate::parse_date_time(df$V1, "HMp mdy")
#[1] "2014-04-14 13:30:00 UTC" "2014-04-14 13:36:00 UTC" "2014-04-14 13:50:00 UTC"
#[4] "2014-04-16 17:30:00 UTC" "2014-04-17 18:40:00 UTC" "2014-04-19 18:46:00 UTC"
data
df <- structure(list(V1 = structure(1:6, .Label = c("1:30 PM 4-14-2014",
"1:36 PM 4-14-2014", "1:50 PM 4-14-2014", "5:30 PM 4-16-2014",
"6:40 PM 4-17-2014", "6:46 PM 4-19-2014"), class = "factor")),
class = "data.frame", row.names = c(NA, -6L))