I'm using Stata 14.2. i have a dataset with dates in a string variable e.g. 01-Apr-2018. I have used the below code to convert them to format them as date variables, however the new date variable that I create is all missing values

Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input str9 dateperformed
"2-Apr-20" 
"2-Aug-18" 
"16-Oct-18"
"8-Jan-19" 
"19-Sep-18"
"11-Oct-18"
"2-Jul-20" 
"29-Oct-18"
"24-Apr-19"
"25-Nov-19"
"10-Sep-19"
"31-Jul-18"
"29-May-18"
"3-Jun-19" 
"18-Dec-18"
"18-Dec-18"
"18-Mar-20"
"21-May-18"
"26-Jun-20"
"9-May-18" 
"21-Aug-19"
"29-Aug-18"
"2-Nov-18" 
"16-Jul-20"
"6-Apr-20" 
"6-Apr-20" 
"23-Jul-19"
"18-Oct-18"
"10-Jul-20"
"18-Sep-19"
"21-Mar-19"
"16-Mar-20"
"21-Jan-20"
"10-Mar-20"
"30-Jul-18"
"29-Aug-18"
end

Code:
. gen date_performed = date(dateperformed, "DMY")
(1,483 missing values generated)

. format %tdDD/NN/CCYY date_performed


Code:
* Example generated by -dataex-. To install: ssc install dataex
clear
input float date_performed
.
.
.
.
.
.
.
.
.
.
.
end
format %tdDD/NN/CCYY date_performed
I have seen similar threads and tried all the fixes I've found but nothing seems to work for my dataset. Can someone advise how to fix the formatting of this date variable?

Thanks