// Arduino Timezone Library Copyright (C) 2018 by Jack Christensen and
// licensed under GNU GPL v3.0, https://www.gnu.org/licenses/gpl.html
//
// Arduino Timezone Library example sketch.
// Self-adjusting clock for multiple time zones.
// Jack Christensen Mar 2012
//
// For time zone information:
// http://www.timeanddate.com/worldclock/

#include <Timezone.h>    // https://github.com/JChristensen/Timezone

// Australia Eastern Time Zone (Sydney, Melbourne)
TimeChangeRule aEDT = {"AEDT", First, Sun, Oct, 2, 660};    // UTC + 11 hours
TimeChangeRule aEST = {"AEST", First, Sun, Apr, 3, 600};    // UTC + 10 hours
Timezone ausET(aEDT, aEST);

// Moscow Standard Time (MSK, does not observe DST)
TimeChangeRule msk = {"MSK", Last, Sun, Mar, 1, 180};
Timezone tzMSK(msk);

// Central European Time (Frankfurt, Paris)
TimeChangeRule CEST = {"CEST", Last, Sun, Mar, 2, 120};     // Central European Summer Time
TimeChangeRule CET = {"CET ", Last, Sun, Oct, 3, 60};       // Central European Standard Time
Timezone CE(CEST, CET);

// United Kingdom (London, Belfast)
TimeChangeRule BST = {"BST", Last, Sun, Mar, 1, 60};        // British Summer Time
TimeChangeRule GMT = {"GMT", Last, Sun, Oct, 2, 0};         // Standard Time
Timezone UK(BST, GMT);

// UTC
TimeChangeRule utcRule = {"UTC", Last, Sun, Mar, 1, 0};     // UTC
Timezone UTC(utcRule);

// US Eastern Time Zone (New York, Detroit)
TimeChangeRule usEDT = {"EDT", Second, Sun, Mar, 2, -240};  // Eastern Daylight Time = UTC - 4 hours
TimeChangeRule usEST = {"EST", First, Sun, Nov, 2, -300};   // Eastern Standard Time = UTC - 5 hours
Timezone usET(usEDT, usEST);

// US Central Time Zone (Chicago, Houston)
TimeChangeRule usCDT = {"CDT", Second, Sun, Mar, 2, -300};
TimeChangeRule usCST = {"CST", First, Sun, Nov, 2, -360};
Timezone usCT(usCDT, usCST);

// US Mountain Time Zone (Denver, Salt Lake City)
TimeChangeRule usMDT = {"MDT", Second, Sun, Mar, 2, -360};
TimeChangeRule usMST = {"MST", First, Sun, Nov, 2, -420};
Timezone usMT(usMDT, usMST);

// Arizona is US Mountain Time Zone but does not use DST
Timezone usAZ(usMST);

// US Pacific Time Zone (Las Vegas, Los Angeles)
TimeChangeRule usPDT = {"PDT", Second, Sun, Mar, 2, -420};
TimeChangeRule usPST = {"PST", First, Sun, Nov, 2, -480};
Timezone usPT(usPDT, usPST);

void setup()
{
    Serial.begin(115200);
    
    // set the system time to UTC
    // warning: assumes that compileTime() returns US EDT
    // adjust the following line accordingly if you're in another time zone
    setTime(compileTime() + 240 * 60);
}

void loop()
{
    time_t utc = now();
    Serial.println();
    printDateTime(ausET, utc, "Sydney");
    printDateTime(tzMSK, utc, " Moscow");
    printDateTime(CE, utc, "Paris");
    printDateTime(UK, utc, " London");
    printDateTime(UTC, utc, " Universal Coordinated Time");
    printDateTime(usET, utc, " New York");
    printDateTime(usCT, utc, " Chicago");
    printDateTime(usMT, utc, " Denver");
    printDateTime(usAZ, utc, " Phoenix");
    printDateTime(usPT, utc, " Los Angeles");
    delay(10000);
}

// Function to return the compile date and time as a time_t value
time_t compileTime()
{
    const time_t FUDGE(10);     // fudge factor to allow for compile time (seconds, YMMV)
    const char *compDate = __DATE__, *compTime = __TIME__, *months = "JanFebMarAprMayJunJulAugSepOctNovDec";
    char chMon[3], *m;
    tmElements_t tm;

    strncpy(chMon, compDate, 3);
    chMon[3] = '\0';
    m = strstr(months, chMon);
    tm.Month = ((m - months) / 3 + 1);

    tm.Day = atoi(compDate + 4);
    tm.Year = atoi(compDate + 7) - 1970;
    tm.Hour = atoi(compTime);
    tm.Minute = atoi(compTime + 3);
    tm.Second = atoi(compTime + 6);
    time_t t = makeTime(tm);
    return t + FUDGE;           // add fudge factor to allow for compile time
}

// given a Timezone object, UTC and a string description, convert and print local time with time zone
void printDateTime(Timezone tz, time_t utc, const char *descr)
{
    char buf[40];
    char m[4];    // temporary storage for month string (DateStrings.cpp uses shared buffer)
    TimeChangeRule *tcr;        // pointer to the time change rule, use to get the TZ abbrev

    time_t t = tz.toLocal(utc, &tcr);
    strcpy(m, monthShortStr(month(t)));
    sprintf(buf, "%.2d:%.2d:%.2d %s %.2d %s %d %s",
        hour(t), minute(t), second(t), dayShortStr(weekday(t)), day(t), m, year(t), tcr -> abbrev);
    Serial.print(buf);
    Serial.print(' ');
    Serial.println(descr);
}