Daylight savings time

// This code is specific for Mountain Time Zone and other time zones that use the same dates.

#include <Wire.h>
#include “RTClib.h” // Library for DS3231 RTC module

RTC_DS3231 rtc;

void setup() {
Serial.begin(9600);
Wire.begin();
rtc.begin();

// If the RTC lost power and lost track of time, set the time to compile time
if (!rtc.isrunning()) {
rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));
}
}

void loop() {
DateTime now = rtc.now();
adjustForDST(now);
printTime(now);
delay(1000); // Update once per second
}

void adjustForDST(DateTime &time) {
int year = time.year();
int month = time.month();
int day = time.day();
int hour = time.hour();

// Adjust for DST if necessary
if (isDST(year, month, day)) {
hour++; // Add one hour for DST
if (hour > 23) {
hour = 0; // Wrap around to 0 if hour exceeds 23
day++; // Move to the next day
}
}

// Update the time object with adjusted values
time = DateTime(year, month, day, hour, time.minute(), time.second());
}

bool isDST(int year, int month, int day) {
// Check if the given date falls within DST period for Mountain Time Zone
if (month < 3 || month > 11) return false; // January, February, and December are definitely not DST months
if (month > 3 && month < 11) return true; // April to October are definitely DST months

// Determine the exact transition dates for DST in Mountain Time Zone
if (month == 3) {
int previousSunday = day – (time.dayOfTheWeek() – 1);
if (day >= 8 && previousSunday <= 14) { // Second Sunday
return (day – previousSunday) >= 7;
}
}
if (month == 11) {
int previousSunday = day – (time.dayOfTheWeek() – 1);
if (day <= 7 && previousSunday >= 1) { // First Sunday
return (day – previousSunday) < 0;
}
}
return false;
}

void printTime(DateTime time) {
// Print the time in HH:MM:SS format
Serial.print(time.hour(), DEC);
Serial.print(‘:’);
if (time.minute() < 10) {
Serial.print(‘0’);
}
Serial.print(time.minute(), DEC);
Serial.print(‘:’);
if (time.second() < 10) {
Serial.print(‘0’);
}
Serial.println(time.second(), DEC);
}

• This reply was modified 8 months ago by  David Fox.