Why I cannot save mutate result in r

Question

This should be a straightforward question. Within each group (name), I attempted to rank "date" and record the rank output as rank date.

"Error in df percent > percent group by(name) percent > percent rank date - mutate(df, rank = order(score,: could not find function " percent > percent -"

df = data.frame(name=c("A","A","A","B","C","D"), score = c("03/21/2021", "04/21/2021", "05/21/2021", "06/21/2021","07/21/2021","03/21/2021"))
df$score = as.Date(df$score,"%m/%d/%Y")
df %>% 
    group_by(name)%>% 
  rank_date<-mutate(df, rank=order(score, decreasing=TRUE))