View raw code<\/a><\/p>\n\n\n\nHow Does the Code Work<\/h3>\n\n\n\n Start by importing the RTCLib<\/span> library.<\/p>\n\n\n\n#include \"RTClib.h\"<\/code><\/pre>\n\n\n\nThen, create an RTC_DS1307<\/span> object called rtc<\/span>.<\/p>\n\n\n\nRTC_DS1307 rtc;<\/code><\/pre>\n\n\n\nIf you’re using a DS3231 RTC module, use the following line instead.<\/p>\n\n\n\n
RTC_DS3231 rtc;<\/code><\/pre>\n\n\n\nThen, you create a char array with the days of the week.<\/p>\n\n\n\n
char daysOfTheWeek[7][12] = {\"Sunday\", \"Monday\", \"Tuesday\", \"Wednesday\", \"Thursday\", \"Friday\", \"Saturday\"};<\/code><\/pre>\n\n\n\nYou can access each day by its index. For example:<\/p>\n\n\n\n
\ndaysOfTheWeek[0]<\/span> will return “Sunday”.<\/li>\n\n\n\ndaysOfTheWeek[1]<\/span> will return “Monday”.<\/li>\n<\/ul>\n\n\n\nIn the setup()<\/span>, initialize the Serial Monitor.<\/p>\n\n\n\nSerial.begin(115200);<\/code><\/pre>\n\n\n\nInitialize the RTC module as follows:<\/p>\n\n\n\n
if (! rtc.begin()) {\n Serial.println(\"Couldn't find RTC\");\n Serial.flush();\n while (1) delay(10);\n}<\/code><\/pre>\n\n\n\nChecking the RTC Status<\/h4>\n\n\n\n Then, check if the RTC is keeping the time with the isrunning()<\/span> function. If it is not running, because it is a new device or because the battery backup failed, we’ll print a message in the Serial Monitor and set the time.<\/p>\n\n\n\nif (! rtc.isrunning()) {\n Serial.println(\"RTC is NOT running, let's set the time!\");<\/code><\/pre>\n\n\n\nSetting the Time<\/h4>\n\n\n\n To set the time on thr RTC, we can use the adjust()<\/span> method on our rtc<\/span> object. The following line sets the RTC\u2019s date and time to the current date and time when this sketch was last compiled.<\/p>\n\n\n\nrtc.adjust(DateTime(F(__DATE__), F(__TIME__)));<\/code><\/pre>\n\n\n\n__DATE__<\/span> and __TIME__<\/span> are macros that provide the current date and time at compilation.<\/p>\n\n\n\nAlternatively, you can set the date and time manually. Pass the time fields in this order: year, month, day, hour, minute, second. This line is commented on the code.<\/p>\n\n\n\n
\/\/ January 21, 2014 at 3am you would call:\nrtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));<\/code><\/pre>\n\n\n\nIf you need to re-set the time on a previously configured device, you can call one of the previous two lines to set the time without checking if it is running or not (this is commented on the code).<\/p>\n\n\n\n
\/\/ When time needs to be re-set on a previously configured device, the\n\/\/ following line sets the RTC to the date & time this sketch was compiled\n\/\/rtc.adjust(DateTime(F(__DATE__), F(__TIME__)));\n\/\/ This line sets the RTC with an explicit date & time, for example to set\n\/\/ January 21, 2014 at 3am you would call:\n\/\/rtc.adjust(DateTime(2014, 1, 21, 3, 0, 0));<\/code><\/pre>\n\n\n\nGetting Date and Time<\/h4>\n\n\n\n In the loop()<\/span>, we get the date and time every three seconds, and we print it in the Serial Monitor.<\/p>\n\n\n\nWe call rtc.now()<\/span> to get the current date and time from the RTC module.<\/p>\n\n\n\nDateTime now = rtc.now();<\/code><\/pre>\n\n\n\nIt returns a DateTime<\/span> object containing the values for the current year, month, day, hour, minute, and second.<\/p>\n\n\n\nTo access each field of the date and time, we can use the following methods:<\/p>\n\n\n\nnow.year()<\/span><\/td> Gets the current year (e.g., 2024)<\/td><\/tr> now.month()<\/span><\/td> Gets the current month (1\u201312)<\/td><\/tr> now.day()<\/span><\/td> Gets the current day of the month (1\u201331)<\/td><\/tr> now.dayOfTheWeek()<\/span><\/td> Gets the day of the week (0-6), where 0 is Sunday, and 6 is Saturday<\/td><\/tr> now.hour()<\/span><\/td> Gets the current hour (0\u201323)<\/td><\/tr> now.minute()<\/span><\/td> Gets the current minute (0\u201359)<\/td><\/tr> now.second()<\/span><\/td> Gets the current second (0\u201359)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\nTo convert the result into a string, we can use the String()<\/span> method. We also pass DEC<\/span> as a second argument to the string()<\/span> method to get a decimal number.<\/p>\n\n\n\nString yearStr = String(now.year(), DEC);<\/code><\/pre>\n\n\n\nIn case of the month, day, hour, minute, and second, we add a leading zero when the number is smaller than 10. So, instead of having, for example: 3:5:6 (which is weird for a time format), you’ll get 03:05:06<\/span>.<\/p>\n\n\n\nString monthStr = (now.month() < 10 ? \"0\" : \"\") + String(now.month(), DEC);\nString dayStr = (now.day() < 10 ? \"0\" : \"\") + String(now.day(), DEC);\nString hourStr = (now.hour() < 10 ? \"0\" : \"\") + String(now.hour(), DEC); \nString minuteStr = (now.minute() < 10 ? \"0\" : \"\") + String(now.minute(), DEC);\nString secondStr = (now.second() < 10 ? \"0\" : \"\") + String(now.second(), DEC);<\/code><\/pre>\n\n\n\nTo get the name of the day of the week, we use the daysOfTheWeek<\/span> array we created at the beginning of the code.<\/p>\n\n\n\nString dayOfWeek = daysOfTheWeek[now.dayOfTheWeek()];<\/code><\/pre>\n\n\n\nIn the end, we concatenate all the time fields in a variable and display it in the Serial Monitor.<\/p>\n\n\n\n
\/\/ Complete time string\nString formattedTime = dayOfWeek + \", \" + yearStr + \"-\" + monthStr + \"-\" + dayStr + \" \" + hourStr + \":\" + minuteStr + \":\" + secondStr;\n\n\/\/ Print the complete formatted time\nSerial.println(formattedTime);<\/code><\/pre>\n\n\n\nTesting the Example<\/h3>\n\n\n\n With the RTC connected to the ESP8266, upload the code to your board.<\/p>\n\n\n\n
Open the Serial Monitor at a baud rate of 115200. The ESP8266 will set the RTC time and will display the current time every three seconds.<\/p>\n\n\n
\n
Syncing the RTC with an NTP Server<\/h2>\n\n\n\n The following example is similar to the previous one, but it syncs the RTC time with an NTP server after connecting the ESP8266 to the internet. This method is useful if there’s a need to reset or adjust the time without manual input, for example, after changing the coin cell of the RTC, or if for some reason the RTC module crashes. In this particular example, we also add the option to synchronize the time with the NTP server every hour to prevent drifts along the time (the periodic sync should be adjusted depending on your project requirements).<\/p>\n\n\n
\/*\n Rui Santos & Sara Santos - Random Nerd Tutorials\n Complete project details at https:\/\/RandomNerdTutorials.com\/esp8266-nodemcu-ds1307-real-time-clock-rtc-arduino\/\n Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files. \n The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.\n*\/\n\n#include <ESP8266WiFi.h>\n#include <time.h>\n#include <RTClib.h>\n\n\/\/ Enter your Wi-Fi credentials\nconst char* ssid = "REPLACE_WITH_YOUR_SSID";\nconst char* password = "REPLACE_WITH_YOUR_PASSWORD";\n\n\/\/ NTP server details\nconst char* ntpServer = "pool.ntp.org";\nconst long gmtOffset_sec = 0; \/\/ Offset for GMT in seconds\nconst int daylightOffset_sec = 3600; \/\/ Daylight savings time in seconds\n\n\/\/ RTC object (for DS1307 or DS3231)\nRTC_DS1307 rtc; \/\/ Change to RTC_DS1307 for DS1307 module\n\nchar daysOfTheWeek[7][12] = {"Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"};\n\n\/\/ Global timeinfo struct and last sync timestamp\nstruct tm timeinfo;\nunsigned long lastSyncMillis = 0; \/\/ Last sync time in milliseconds\n\nvoid setup() {\n Serial.begin(115200);\n initWiFi();\n\n \/\/ Initialize RTC\n if (!rtc.begin()) {\n Serial.println("Couldn't find RTC");\n while (1);\n }\n\n \/\/ Sync the RTC at startup\n syncTime();\n}\n\nvoid loop() {\n checkTimeAndSync(); \/\/ Check if 1 hour has passed and sync if necessary\n\n \/\/ Get current time from RTC\n DateTime now = rtc.now();\n\n \/\/ Getting each time field in individual variables\n String yearStr = String(now.year(), DEC);\n String monthStr = (now.month() < 10 ? "0" : "") + String(now.month(), DEC);\n String dayStr = (now.day() < 10 ? "0" : "") + String(now.day(), DEC);\n String hourStr = (now.hour() < 10 ? "0" : "") + String(now.hour(), DEC);\n String minuteStr = (now.minute() < 10 ? "0" : "") + String(now.minute(), DEC);\n String secondStr = (now.second() < 10 ? "0" : "") + String(now.second(), DEC);\n String dayOfWeek = daysOfTheWeek[now.dayOfTheWeek()];\n\n \/\/ Complete time string\n String formattedTime = dayOfWeek + ", " + yearStr + "-" + monthStr + "-" + dayStr + " " + hourStr + ":" + minuteStr + ":" + secondStr;\n\n \/\/ Print the complete formatted time\n Serial.println(formattedTime);\n\n Serial.println();\n delay(10000);\n}\n\nvoid initWiFi() {\n WiFi.begin(ssid, password); \/\/ Connect to WiFi\n while (WiFi.status() != WL_CONNECTED) {\n delay(500);\n Serial.print(".");\n }\n Serial.println("\\nWiFi connected.");\n}\n\nvoid syncTime() {\n configTime(gmtOffset_sec, daylightOffset_sec, ntpServer); \/\/ Configure time with NTP server\n if (!getLocalTime(&timeinfo)) {\n Serial.println("Failed to obtain time");\n return;\n }\n Serial.println("\\nESP8266 Time synchronized with NTP server.");\n\n \/\/ Format the current time as a string\n char timeStr[64];\n strftime(timeStr, sizeof(timeStr), "%A, %B %d %Y %H:%M:%S", &timeinfo);\n Serial.print("Current time: ");\n Serial.println(timeStr);\n\n \/\/ Sync the RTC with the NTP time\n rtc.adjust(DateTime(timeinfo.tm_year + 1900, timeinfo.tm_mon + 1, timeinfo.tm_mday,\n timeinfo.tm_hour, timeinfo.tm_min, timeinfo.tm_sec));\n\n lastSyncMillis = millis(); \/\/ Record the last sync time in milliseconds\n}\n\nvoid checkTimeAndSync() {\n \/\/ Check if 1 hour has passed since the last sync (1 hour = 3600000 milliseconds)\n if (millis() - lastSyncMillis >= 3600000) {\n Serial.println("Synchronizing time with NTP...");\n syncTime();\n }\n}\n<\/code><\/pre>\n\tView raw code<\/a><\/p>\n\n\n\nHow Does the Code Work?<\/h3>\n\n\n\n This code is similar to the previous one, but uses an NTP server to sync the time. To get time from an NTP server, the ESP8266 needs to be connected to the internet.<\/p>\n\n\n\n
First, you need to include the following libraries.<\/p>\n\n\n\n
#include <ESP8266WiFi.h>\n#include <time.h>\n#include <RTClib.h><\/code><\/pre>\n\n\n\nThen, you need to insert your network connections in the following lines.<\/p>\n\n\n\n
\/\/ WiFi credentials\nconst char* ssid = \"REPLACE_WITH_YOUR_SSID\";\nconst char* password = \"REPLACE_WITH_YOUR_PASSWORD\";<\/code><\/pre>\n\n\n\nNext we have the NTP server details. The NTP server returns the time in GMT. If you’re on a different time zone, you can add the time zone offset on the gmtOffset_sec<\/span> variable in seconds. Also add daylight saving time in seconds in the daylightOffset_sec<\/span> variable if needed.<\/p>\n\n\n\n\/\/ NTP server details\nconst char* ntpServer = \"pool.ntp.org\";\nconst long gmtOffset_sec = 0; \/\/ Offset for GMT in seconds\nconst int daylightOffset_sec = 3600; \/\/ Daylight savings time in seconds<\/code><\/pre>\n\n\n\nWe create a tm<\/span> structure called timeinfo<\/span> to save the time from the NTP server.<\/p>\n\n\n\nstruct tm timeinfo;<\/code><\/pre>\n\n\n\nThe tm<\/span> structure contains a calendar date and time broken down into its components:<\/p>\n\n\n\n\ntm_sec<\/span>: seconds after the minute;<\/li>\n\n\n\ntm_min<\/span>: minutes after the hour;<\/li>\n\n\n\ntm_hour<\/span>: hours since midnight;<\/li>\n\n\n\ntm_mday<\/span>: day of the month;<\/li>\n\n\n\ntm_year<\/span>: years since 1900;<\/li>\n\n\n\ntm_wday<\/span>: days since Sunday;<\/li>\n\n\n\ntm_yday<\/span>: days since January 1;<\/li>\n\n\n\ntm_isdst<\/span>: Daylight Saving Time flag;<\/li>\n\n\n\ntm structure documentation<\/a>.<\/li>\n<\/ul>\n\n\n\nTo learn more about getting time from an NTP server with the ESP8266, check out this tutorial: Get Date and Time with ESP8266 NodeMCU NTP Client-Server<\/a>.<\/p>\n\n\n\nWe create a variable to save the time that has passed since we synchronized the time.<\/p>\n\n\n\n
unsigned long lastSyncMillis = 0; \/\/ Last sync time in milliseconds<\/code><\/pre>\n\n\n\nIn the setup()<\/span>, we intialize the Serial Monitor and connect the ESP8266 to Wi-Fi.<\/p>\n\n\n\nvoid setup() {\n Serial.begin(115200);\n initWiFi();<\/code><\/pre>\n\n\n\nWe initialize the RTC module.<\/p>\n\n\n\n
\/\/ Initialize RTC\nif (!rtc.begin()) {\n Serial.println(\"Couldn't find RTC\");\n while (1);\n}<\/code><\/pre>\n\n\n\nAnd finally, we call the syncTime()<\/span> function, declared at the end of the code, to synchronize the time.<\/p>\n\n\n\n\/\/ Sync the RTC at startup\nsyncTime();<\/code><\/pre>\n\n\n\nThe syncTime() function<\/h4>\n\n\n\n On the syncTime()<\/span> function, we get the time from the NTP server and save it on the timeinfo<\/span> variable.<\/p>\n\n\n\nconfigTime(gmtOffset_sec, daylightOffset_sec, ntpServer); \/\/ Configure time with NTP server\nif (!getLocalTime(&timeinfo)) {\n Serial.println(\"Failed to obtain time\");\n return;\n}<\/code><\/pre>\n\n\n\nThen, we call the rtc.adjust()<\/span> method and pass as arguments the time fields from the timeinfo<\/span> variable. This will synchronize the RTC time with the time from the NTP server.<\/p>\n\n\n\n\/\/ Sync the RTC with the NTP time\nrtc.adjust(DateTime(timeinfo.tm_year + 1900, timeinfo.tm_mon + 1, timeinfo.tm_mday,\n timeinfo.tm_hour, timeinfo.tm_min, timeinfo.tm_sec));<\/code><\/pre>\n\n\n\n
![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/11\/ESP8266-DS1307-RTC-Guide.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"DS1307](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/10\/DS1307-RTC-Module.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"DS1307](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/10\/DS1307-battery-holder-2.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure>\n<\/div>\n\n\n\n![\"DS1307](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/10\/DS1307-battery-holder.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure>\n<\/div>\n<\/div>\n\n\n\n![\"RTC](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/11\/RTC-I2C-scanner-addresses.png?resize=671%2C252&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/11\/ESP8266-RTC-Circuit_bb.png?resize=786%2C539&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"Arduino](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/11\/install-RTCLib.png?resize=750%2C391&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"ESP8266](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/11\/ESP8266-with-DS1307-RTC.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n![\"ESP32](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2024\/11\/esp8266-set-and-read-time-RTC.png?resize=666%2C264&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n