I want to set a flag when a user enters a datetime which is either before 10 minutes from now or after 10 minutes from now.
I have tried many possibilities but I am not getting the proper result. Can anyone help me please.   
   
    Error message : ValueError: time data '' does not match format '%Y-%m-%d %H:%M:%S'
   
    py file :    
    @api.multi
    def write(self, values):
        check_out = values.get('check_out', '')
        log_in = values.get('log_in', '')
        log_out = values.get('log_out', '')
        check_in = values.get('check_in', '')
        import datetime
        now = datetime.datetime.now()
        d = now.replace(microsecond=0)
        my_login_time = datetime.datetime.strptime(log_in, '%Y-%m-%d %H:%M:%S')
        my_logout_time = datetime.datetime.strptime(log_out, '%Y-%m-%d %H:%M:%S')
        start_time = d - datetime.timedelta(minutes=10)
        end_time = d + datetime.timedelta(minutes=10)
        if check_in:           
            if my_login_time > end_time or my_login_time < start_time:
                self.set_flag = True
        if check_out:
            if my_logout_time > end_time or my_logout_time < start_time:
                self.set_flag = True
        res = super(AgendaLine, self).write(values)
        return res