iOS - Not able to store NSDate into NSUserDefaults -

in application, want store date @ app started first time.
i'm using following code in application:didfinishlaunchingwithoptions method

nsdate* today = [nsdate date]; [[nsuserdefaults standarduserdefaults] registerdefaults: @{@"conscience_start_date" : today}];  nslog(@"%@", [[nsuserdefaults standarduserdefaults] objectforkey:@"conscience_start_date"]); 

but every time when start application, printing time @ app starting. not printing date @ started app.

i tried reset simulator , ran code again. still no success. can 1 point me error in code please?

since goal keep track of first time user starts app, need in application:didfinishlaunchingwithoptions:

nsdate *date = [[nsuserdefaults standarduserdefaults] objectforkey:@"conscience_start_date"]; if (!date) {     // 1st run of app     date = [nsdate date];     [[nsuserdefaults standarduserdefaults] setobject:date forkey:@"conscience_start_date"]; // save date }  nslog(@"first run %@", date);