Without an RTC the Arduino won't know what time it is. It will need a time from the outside, e.g. via a WiFi module or supplied by an external computer over the serial port. Since you're having it connected to the PC all the time I would just write a small Python script that reads the serial port, adds a timestamp, and writes it to the log file. I'm not familiar with PuTTy (it's a windows program, I use Linux) but going via PuTTy seems like a lot of extra work if you want timestamps. Answer from radome9 on reddit.com
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Arduino Forum
forum.arduino.cc › projects › programming
Get Date and Time Without RTC Shields - Programming - Arduino Forum
August 4, 2016 - I'm trying to get the Arduino Uno or Mega to print the date and time onto the serial monitor. All the tutorial requires a RTC hardware add-on such as an adafruit data logger. Is there a way to do this with coding alone?
Discussions

arduino uno - Can I simulate a clock without an RTC connected? - Arduino Stack Exchange
I want to program for a timer that works as set timer such as in an oven where user can set their own time. One of the way I know is using an IC(RTC) for the timer. However, I don't have the IC yet... More on arduino.stackexchange.com
🌐 arduino.stackexchange.com
May 15, 2018
I tested Arduino time keeping without RTC
Hey everyone, If anyone here is wondering how well an arduino or esp8266 keeps track of time on its own, I tested it for you: link Spoiler: only about one second off every day. Any suggestions on improving the code would be more than welcome. I just read that millis() resets every 50 days, ... More on forum.arduino.cc
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15
0
May 22, 2016
Use Time.h without a hardware RTC?
Can someone provide some clarity about this? I want to use the RTC functions in the Time library to create an RTC whose accuracy is a "don't care", I just need something to allow me to use "now()" and give me relative time stamps while running and debugging code that is event driven. More on forum.arduino.cc
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6
0
March 29, 2022
Add current time (changing) without RTC
I am making a weather station and am registering some data hourly, which is shown on the serial monitor. I need to display the current time and date every time I post the temperature etc. I do not have an RTC and I won't buy one. I have tried using __ TIME __ but apparently, that time doesn't ... More on forum.arduino.cc
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10
0
November 1, 2023
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Instructables
instructables.com › circuits › arduino
Timekeeping on ESP8266 & Arduino Uno WITHOUT an RTC (Real Time CLock)? : 3 Steps - Instructables
September 28, 2017 - Timekeeping on ESP8266 & Arduino Uno WITHOUT an RTC (Real Time CLock)? : Like the title says, I have tested keeping track of time on my arduino uno and the ESP8266 / Wemos D1 boards(programmed with arduino) WITHOUT the use of libraries, internet or an RTC unit.
Top answer
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TimeLib.h has a virtual clock that can be updated and corrected from multiple sources, including an RTC chip or an NTP server on the internet (assuming an internet connection).

It doesn't need that clock source, though, but it will drift with time. Once you have set the clock correctly it will keep close to the right time (assuming no reset or power loss of the Arduino). Not perfect (because the Arduino's main clock isn't perfect) but close enough for many simple applications.

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There are programs to simulate Arduino code, but they are very limited. To really simulate the circuit the program would have to also know about the IC you are using. You didn't told us what IC this is, so we can only speculate, that it might not be something, that these programs know (though you can try it). And sometimes Arduino Simulators have problems with simulating time sensitive code. If you want to try, just google for Arduino Simulator and check out the possibilities. I cannot suggest one, since I didn't use one until now.

At this point it might be the better option to write time-keeping code using the millis() function, which returns the number of milliseconds since the Arduino started. Save a timestamp from when you started and compare the difference between millis() and your timestamp to the wanted bake time.

You can pack this code in extra functions, that can later be replaced by code managing the "timer IC". With dividing your code this way you can write the rest of the logic without bothering about the timing part (after writing the millis() part as a "dummy").

For an oven timer the accuracy of the Arduinos clock should be ok, since it doesn't really matter, if it is a few seconds off. And for testing and writing the first code version it is also sufficient.


If the IC you are referring to is a RTC (Real Time Clock) module, the code for it should be pretty simple to write. There are libraries for the most common RTCs. You might want to try the Arduino Time library.

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ResearchGate
researchgate.net › publication › 354250100_Arduino_Digital_Clock_without_RTC_Module
Arduino Digital Clock without RTC Module
June 5, 2026 - It enables us to modify the time using a keypad and LCD without an external device. Continuous power is supplied to the Arduino using a battery backup. Such a circuit is simple with reduced code.
Find elsewhere
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Arduino
projecthub.arduino.cc › ahmadordi › clock-without-using-rtc-in-arduino-with-temperature-and-humi-725aaa
Clock without using RTC in Arduino with Temperature and humi | Arduino Project Hub
1// Ahmad Ordikhani Seyedlar 2 3#include <LiquidCrystal.h> 4#include <SimpleDHT.h> 5 6// initialize the library with the numbers of the interface pins 7LiquidCrystal lcd(7, 8, 9, 10, 11, 12); 8volatile int sec, minute = 0, hour = 0; 9int b_h = 5; 10int b_m = 6; 11int pinDHT11 = 2; 12int b_startstop = 3; 13bool startstop = false; 14 15SimpleDHT11 dht11; 16 17void setup() { 18 19 // set up the LCD's number of columns and rows: 20 lcd.begin(16, 2); 21 22 lcd.setCursor(0, 0); 23 lcd.print("Ahmad Ordikhani"); 24 lcd.setCursor(0, 1); 25 lcd.print("Clk without RTC"); 26 delay(3000); 27 lcd.clear(); 2
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Arduino Forum
forum.arduino.cc › projects › programming
I tested Arduino time keeping without RTC - Programming - Arduino Forum
May 22, 2016 - Hey everyone, If anyone here is wondering how well an arduino or esp8266 keeps track of time on its own, I tested it for you: link Spoiler: only about one second off every day. Any suggestions on improving the code would be more than welcome. I just read that millis() resets every 50 days, ...
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Instructables
instructables.com › circuits › arduino
Arduino Digital Clock Without RTC Real Time Clock Module on Tinkercad : 4 Steps (with Pictures) - Instructables
April 12, 2024 - Arduino Digital Clock Without RTC Real Time Clock Module on Tinkercad: In this project, I made a simple Digital Clock using Arduino without using RTC Module and built the simulator on Tinkercad environment. This project is Arduino digital clock without using real-time clock module.
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Arduino Forum
forum.arduino.cc › projects › programming
Use Time.h without a hardware RTC? - Programming - Arduino Forum
March 29, 2022 - Can someone provide some clarity about this? I want to use the RTC functions in the Time library to create an RTC whose accuracy is a "don't care", I just need something to allow me to use "now()" and give me relative t…
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Arduino
projecthub.arduino.cc › plouc68000 › simplest-uno-digital-clock-ever-03c185
Simplest UNO Digital Clock Ever | Arduino Project Hub
The simplest Arduino LCD clock ever designed. Only needs an Arduino UNO, a 1602 LCD, and two buttons. No resistors, no potentiometer.
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Hackster.io
hackster.io › kabirajabhirup › alarm-clock-without-rtc-697ffb
Alarm clock without RTC - Hackster.io
August 23, 2022 - #include <LiquidCrystal.h> //#include <DHT.h> /*================================ LCD INPUTS ================================*/ int rs = 7; int en = 8; int d4 = 9; int d5 = 10; int d6 = 11; int d7 = 12; LiquidCrystal lcd(rs, en, d4, d5, d6, d7); /*================================== TIME/ALARM SETTER ===================================*/ int timeset = A3; int secs, mins, hour; int alarm=A1; int hour1,min1; int buzzpin=6; void setup() { Serial.begin(9600); // put your setup code here, to run once: lcd.begin(16, 2); pinMode(buzzpin,OUTPUT); digitalWrite(buzzpin,LOW); pinMode(timeset,INPUT); pinMod
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Amazon
amazon.com › Arduino-Clock-Without-Module-Tinkercad-ebook › dp › B0C5NQ22PD
Arduino Clock Without RTC Module on Tinkercad: Build Arduino Digital Clock With No Real Time Clock Module (Arduino Tinkercad Projects for Beginners and Hobbyists), Ebeed, Ahmed, eBook - Amazon.com
Arduino Clock Without RTC Module on Tinkercad: Build Arduino Digital Clock With No Real Time Clock Module (Arduino Tinkercad Projects for Beginners and Hobbyists) - Kindle edition by Ebeed, Ahmed. Download it once and read it on your Kindle device, PC, phones or tablets.
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Electronic Wings
electronicwings.com › users › SoumyajoyDebnath › projects › 1406 › digital-clock-using-arduino-uno-without-rtc-module
Digital Clock using Arduino UNO Without RTC module | project
It has 20 digital input/output pins (of which 6 can be used as PWM outputs and 6 can be used as analog inputs), a 16 MHz resonator, a USB connection, a power jack, an in-circuit system programming (ICSP) header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC to DC adapter or battery to get started. Programs can be loaded on to it from the easy-to-use Arduino computer program.
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Adafruit
blog.adafruit.com › 2017 › 08 › 21 › simple-arduino-digital-clock-without-rtc
Simple Arduino Digital Clock Without RTC
September 26, 2024 - A great beginners project by Techno on Hackster.io It’s just a simple digital clock controlled by Arduino without using any RTC module (Real Time Clock). Every time you switch on this clock y…
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CircuitDigest
circuitdigest.com › microcontroller-projects › digital-clock-using-arduino-without-rtc-module
Digital Clock using Arduino UNO without RTC Module
December 23, 2022 - The AM and PM format will be automatically set on the basis of 24 hours configuration. I2C module is connected with Arduino sensor shield through TX(0) and RX(1) pin with SDA and SCL pins.
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Arduino
projecthub.arduino.cc › harshitmehra2007 › arduino-clock-without-rtc-with-temperature-and-humidity-c2f9bd
Arduino Clock (without rtc) with temperature and humidity | Arduino Project Hub
This project is a arduino clock made without using an rtc and it is totally accurate it also displays the temperature and the humidity
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Arduino Forum
forum.arduino.cc › projects › programming
Add current time (changing) without RTC - Programming - Arduino Forum
November 1, 2023 - I am making a weather station and am registering some data hourly, which is shown on the serial monitor. I need to display the current time and date every time I post the temperature etc. I do not have an RTC and I won't buy one. I have tried using __ TIME __ but apparently, that time doesn't ...
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Arduino Forum
forum.arduino.cc › projects › general guidance
Digital Alarm Clock without using an RTC - General Guidance - Arduino Forum
February 8, 2019 - Hi, Wondering if it's possible to code a Digital alarm clock using just an Aruino Uno, an LCD screen and some pushbuttons? There's lots of help on creating an alarm clock using an RTC, but I want to try it without as I…