@ch,
Use format.Date function to convert one format of date to another format.
EX:
superstore = read.csv("C:\\Users\\Cherukuri_Sindhu\\Downloads\\global_superstore.csv",stringsAsFactors = FALSE)
#general function to convert date from charater data type to date type.
as.Date.character(superstore$Order.Date,format = "%d-%m-%Y")
#use format function to change date to a different format.
format.Date(superstore$Order.Date,"%d/%m/%Y")