Time span in Tibble

I have a list of records of cars per hour that I summarise per day. I would like also for each day to record the hour of the first and last record.

I am trying this:

data_per_day <- data_per_hour %>%
  group_by(date_loc = lubridate::date(date_loc)) %>% 
  summarise(sum_cars = sum(car),
            count_start = min(hour(date_loc)),
            count_last = max(hour(date_loc)),
            year_day = yday(first(date_loc)))

However, count_start and count_last are always 0.

What am I doing wrong?

The following solution worked:

data_per_day <- data_per_hour %>%
  group_by(date_loc_dt = lubridate::date(date_loc)) %>% 
  summarise(sum_cars = sum(car),
            count_start = min(hour(date_loc)),
            count_last = max(hour(date_loc)),
            year_day = yday(first(date_loc)))

The previous code was overwriting date_loc. Using the new variable date_loc_dt solved the issue.

Thank you to @JonSpring for confirmation.