Solution: Overload a Function

import std.stdio;
struct TimeOfDay {
    int hour;
    int minute;
}
void info(TimeOfDay time) {
    writef("%02s:%02s", time.hour, time.minute);
}
TimeOfDay addDuration(TimeOfDay start,
                      TimeOfDay duration) {
    TimeOfDay result;
    result.minute = start.minute + duration.minute;
    result.hour = start.hour + duration.hour;
    result.hour += result.minute / 60;
    result.minute %= 60;
    result.hour %= 24;
    return result;
}
struct Meeting {
    string    topic;
    size_t    attendanceCount;
    TimeOfDay start;
    TimeOfDay end;
}
void info(Meeting meeting) {
    info(meeting.start);
    write('-');
    info(meeting.end);
    writef(" \"%s\" meeting with %s attendees",
           meeting.topic,
           meeting.attendanceCount);
}
struct Meal {
    TimeOfDay time;
    string    address;
}
void info(Meal meal) {
    info(meal.time);
    write('-');
    info(addDuration(meal.time, TimeOfDay(1, 30)));
    write(" Meal, Address: ", meal.address);
}
struct DailyPlan {
    Meeting amMeeting;
    Meal    lunch;
    Meeting pmMeeting;
}
void info(DailyPlan plan) {
    info(plan.amMeeting);
    writeln();
    info(plan.lunch);
    writeln();
    info(plan.pmMeeting);
}
void main() {
    immutable bikeRideMeeting = Meeting("Bike Ride", 4,
                                        TimeOfDay(10, 30),
                                        TimeOfDay(11, 45));
    immutable lunch = Meal(TimeOfDay(12, 30), "İstanbul");
    immutable budgetMeeting = Meeting("Budget", 8,
                                      TimeOfDay(15, 30),
                                      TimeOfDay(17, 30));
    immutable todaysPlan = DailyPlan(bikeRideMeeting,
                                     lunch,
                                     budgetMeeting);
    info(todaysPlan);
    writeln();
}