How to convert NSDate to NSString?

converting NSDate to NSString creates a memory leak can anyone help.

Here is my code:-

NSDate *today = [[NSDate alloc]init];
NSDateFormatter *df = [[NSDateFormatter alloc] init];
[df setDateFormat:@"yyyy-MM-dd"];
dateString = nil;
dateString =[[NSString alloc]initWithString:[df stringFromDate:today]];
[df setDateFormat:@"EEEE       MMM dd yyyy"];
[dateButton setTitle:[df stringFromDate:today] forState:UIControlStateNormal];
[df release];
[today release];