You need to use the parseDate() function and define the format of the input. According to date tokens, the function should look like (for better understanding, I used the example from your question directly in the function) :
parseDate('Wednesday, 30 August', 'dddd, D MMMM', 'Prague/Europe')
dddd stays for day in a week
D stays for the day in a month, and
MMMM stays for the month’s name
Prague/Europe is the timezone of the date, this is to ensure that the date is correctly parsed
When setting up the function, ensure, that you enter the timezone in which your system works.