todate.Rdtodate converts any POSIXct format variables in the dataframe to date format
todate(dfname)is the name of the dataframe on which to perform the action
Nothing is returned from todate, the action is simply perfomed on the columns of
dataframe dfname
Note that this function will mainly apply to dataframes imported using the read_excel function
from the readxl package. Dataframes imported using, for example, read.csv instead
will have dates in character format and therefore todate will not apply.