Code

Create an rtc_module struct and add to the main application source file, outside of any functions:

struct rtc_module rtc_instance;

The following must be added to the user application:

Function for setting up the module:

void configure_rtc_calendar(void)
{
    /* Initialize RTC in calendar mode. */
    struct rtc_calendar_config config_rtc_calendar;
    rtc_calendar_get_config_defaults(&config_rtc_calendar);

    alarm.time.year      = 2013;
    alarm.time.month     = 1;
    alarm.time.day       = 1;
    alarm.time.hour      = 0;
    alarm.time.minute    = 0;
    alarm.time.second    = 4;

    config_rtc_calendar.clock_24h = true;
    config_rtc_calendar.alarm[0].time = alarm.time;
    config_rtc_calendar.alarm[0].mask = RTC_CALENDAR_ALARM_MASK_YEAR;

    rtc_calendar_init(&rtc_instance, RTC, &config_rtc_calendar);

    rtc_calendar_enable(&rtc_instance);
}

Callback function:

void rtc_match_callback(void)
{
    /* Do something on RTC alarm match here */
    port_pin_toggle_output_level(LED_0_PIN);

    /* Set new alarm in 5 seconds */
    alarm.mask = RTC_CALENDAR_ALARM_MASK_SEC;

    alarm.time.second += 5;
    alarm.time.second = alarm.time.second % 60;

    rtc_calendar_set_alarm(&rtc_instance, &alarm, RTC_CALENDAR_ALARM_0);
}

Function for setting up the callback functionality of the driver:

void configure_rtc_callbacks(void)
{
    rtc_calendar_register_callback(
            &rtc_instance, rtc_match_callback, RTC_CALENDAR_CALLBACK_ALARM_0);
    rtc_calendar_enable_callback(&rtc_instance, RTC_CALENDAR_CALLBACK_ALARM_0);
}

Add to user application main():

system_init();

struct rtc_calendar_time time;
rtc_calendar_get_time_defaults(&time);
time.year   = 2012;
time.month  = 12;
time.day    = 31;
time.hour   = 23;
time.minute = 59;
time.second = 59;

/* Configure and enable RTC */
configure_rtc_calendar();

/* Configure and enable callback */
configure_rtc_callbacks();

/* Set current time. */
rtc_calendar_set_time(&rtc_instance, &time);