void handle_minute_tick(AppContextRef ctx, PebbleTickEvent *t)
{
    /* Need to be static because pointers to them are stored in the text
    * layers.
    */
    static char day_text[] = "XXX";
    static char month_text[] = "XXX";
    static char daynum_text[] = "00";
    static char hour_text[] = "00";
    static char minute_text[] = "00";

    (void)ctx;  /* prevent "unused parameter" warning */

    if (t->units_changed & DAY_UNIT)
    {
        string_format_time(day_text,
                           sizeof(day_text),
                           "%a",
                           t->tick_time);
        string_format_time(month_text,
                           sizeof(month_text),
                           "%b",
                           t->tick_time);
        string_format_time(daynum_text,
                           sizeof(daynum_text),
                           "%d",
                           t->tick_time);
        upcase(day_text);
        upcase(month_text);
        date_layer_set_text(&date_layer, day_text, month_text, daynum_text);
    }