How can I make one letter appear on calendar instead of two for example MO I want to be M. I have tried useWeekdaysShort that makes three letters "MON", Does somebody know how to make "M"
You can read just first character of string you get.
const date = datepicker.getDate();
console.log(date[0]);
If you using react-datepicker library from hackerOne, just write formatWeekDay.
<Datepicker
formatWeekDay={(nameOfDay) => nameOfDay.substr(0, 1)}
/>
Then you can see S M T W T F S.