how to extract date in R code example

Example: extract year from date in r

#create data frame
df <- data.frame(date=c("02/10/2021", "03/07/2020" , "14/03/2021"),
                  sales=c(21, 36, 38))

#view data frame
df

        date 	sales
1 02/10/2021    21
2 03/07/2020    36
3 14/03/2021    38

#create new variable that contains year
df$year <- format(as.Date(df$date, format="%d/%m/%Y"),"%Y")