How to format a (date) string

Projects General Guidance
1

Hello folks,
I'm wondering what would be the best way to (convert and) format date information into a string for output?

e.g. with the help of char str[11] variable?

// format a date into a string with leading zeros (if needed) on nDay and nMonth.

void setup() {
int nDay = 8;
int nMonth = 4;
int nYear = 2025;

Serial.print("today is: ");
Serial.print(nDay);
Serial.print("-");
Serial.print(nMonth);
Serial.print("-");
Serial.print(nYear);
Serial.println();
// expected output: [today is 08-04-2025]
// I know, the code is not doing that. It's just for demonstration

}

void loop () {
  ;
}

Any ideas or suggestions?
Thanks in advance

2 
// format a date into a string with leading zeros (if needed) on nDay and nMonth.

void setup()
{
    Serial.begin(115200);
    int nDay = 8;
    int nMonth = 4;
    int nYear = 2025;

    char buffer[40];  //large enough to hold the output string
    snprintf(buffer, sizeof(buffer), "today is: %02d-%02d-%04d", nDay, nMonth, nYear);
    Serial.println(buffer);
}

void loop()
{
}

I will leave you to research how the formatting works

3 Likes
3

Can You define good, better and the best?

4

Not sure what you mean by 'best way'. There are all sorts of libraries, examples, tutorials about the programers nemisis, dates.
I would look in the Arduino.cc HERE then search like THIS

Screenshot 2025-05-22 at 20.28.26
Screenshot 2025-05-22 at 20.28.261796×466 34.9 KB

NOTICE: bottom right, 16 libraries found. It looks to me like 4 to 6 might be of interest to you.

5

If I really have to answer your question, my answer would be:
good: it's working w/o any errors
better: it's working w/o errors, memory- and time efficient
the best: no further improvement possible.

But someone else might have different criteria.
I'm answering just for the fun of it.

6

Sweet.
I see I still can learn a lot more about C++.
That's the solution for me.
Thanks.

7

Thanks for the tip.
IMHO, its' more about string formatting than dates and times.

8

Not sure what your point is, anytime someone mentions date/time, it's 99% of the time about formatting it.
I hope you found an answer in all the informative posts.