C++ timed events notifier

#include <cstdlib>
#include <string>
#include <ctime>
#include <thread>
#include <chrono>
#include <fstream>
#include <sstream>
#include <vector>

namespace time_constant
{
    const std::string days[7] = { "Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday" };
    constexpr unsigned short day = 0, warn_time = 1, start_time = 2, end_time = 3, warn_title = 4, warn_msg = 5, start_title = 6, start_msg = 7, end_title = 8,
                             end_msg = 9, warning_title = 10, warning_msg = 11, progress_title = 12, progress_msg = 13;
    constexpr unsigned short warn = 0, start = 1, end = 2;
    const std::string cmd = "notify-send";
}

void load_events(std::vector<std::vector<std::string>> &);
void event_loop(std::vector<std::vector<std::string>> &, const bool);

int main(int argc, char *argv[])
{
    if (argc != 2) return -1;
    bool loop = false;
    {
        std::string arg = argv[1];
        if (arg == "loop")
        {
            loop = true;
            std::system((time_constant::cmd + " \"Event Loop\" \"Event loop has started.\"").c_str());
        }
        else if (arg == "now") loop = false;
        else return -1;
    }

    std::vector<std::vector<std::string>> events;
    load_events(events);

    event_loop(events, loop);

    return 0;
}

void load_events(std::vector<std::vector<std::string>> &events)
{
    std::ifstream times("notify-time-conf");
    std::string line;
    while (std::getline(times, line))
    {
        std::stringstream stream(line);
        std::vector<std::string> event;
        std::string word;
        while (stream >> word)
        {
            if (word.find('+') != std::string::npos)
                for (char &c : word)
                    if (c == '+') c = ' ';
            event.push_back(word);
        }
        events.push_back(event);
    }
    times.close();
}

void event_loop(std::vector<std::vector<std::string>> &events, const bool loop)
{
    do
    {
        std::time_t t = std::time(0);
        struct tm *now = std::localtime(&t);
        const unsigned daily_time = now->tm_hour * 3600 + now->tm_min * 60 + now->tm_sec;
        std::string weekday = time_constant::days[now->tm_wday];

        for (const std::vector<std::string> event : events)
        {
            if (event[time_constant::day] == weekday)
            {
                const std::string time_parse[3] = { event[time_constant::warn_time], event[time_constant::start_time], event[time_constant::end_time] };
                unsigned time[3] = { 0 };
                {
                    unsigned short index = 0;
                    for (const std::string s : time_parse)
                    {
                        std::string hour = s.substr(0, 2), minute = s.substr(3, 2);
                        if (hour[0] == '0') hour.erase(0,1);
                        if (minute[0] == '0') minute.erase(0,1);
                        time[index] = std::stoul(hour) * 3600 + std::stoul(minute) * 60;
                        ++index;
                    }
                }
                if (loop)
                {
                    if (daily_time == time[time_constant::warn])
                        std::system((time_constant::cmd + " \"" + event[time_constant::warn_title] + "\" " + "\"" + event[time_constant::warn_msg] + "\" ").c_str());
                    else if (daily_time == time[time_constant::start])
                        std::system((time_constant::cmd + " \"" + event[time_constant::start_title] + "\" " + "\"" + event[time_constant::start_msg] + "\" ").c_str());
                    else if (daily_time == time[time_constant::end])
                        std::system((time_constant::cmd + " \"" + event[time_constant::end_title] + "\" " + "\"" + event[time_constant::end_msg] + "\" ").c_str());
                }
                else
                {

                    if (daily_time >= time[time_constant::warn] && daily_time < time[time_constant::start])
                        std::system((time_constant::cmd + " \"" + event[time_constant::warning_title] + "\" " + "\"" + event[time_constant::warning_msg] + "\" ").c_str());
                    else if (daily_time >= time[time_constant::start] && daily_time < time[time_constant::end])
                        std::system((time_constant::cmd + " \"" + event[time_constant::progress_title] + "\" " + "\"" + event[time_constant::progress_msg] + "\" ").c_str());
                }
            }
        }
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }
    while (loop);
}