use sqlite check to validate whether date with proper format is entered in the column

I have created a table as below:

CREATE TABLE case_status(data_entry_timestamp DATETIME DEFAULT (datetime('now','localtime')) NOT NULL,
                         case_number TEXT PRIMARY KEY NOT NULL, 
                         case_name TEXT DEFAULT MISSING, 
                         death_reportdate DATE CONSTRAINT death_reportdate_chk CHECK (death_reportdate==strftime('%Y-%m-%d',death_reportdate)),
                         );

The column death_reportdate need to have a date with pre-defined format (e.g. 2000-12-31). I created the table, inserted some rows of data, and then try to modified data in death_reportdate, the check rule seems to be bypassed when I enter some random string to it.

What have I done wrong?