Hi.
You can use an RTC module with a coin cell to keep track of time.
We have a tutorial for Arduino. I guess it should be similar for the ESP32:

Guide for Real Time Clock (RTC) Module with Arduino (DS1307 and DS3231)

This tutorial was written a long time ago, so it’s not much complete.
I hope this helps.
Regards,
Sara

Thanks.  I connected an RTC and will see how it goes.

Hi Sara   In this tutorial, the code uses byte pointer variables which are converted to decimals in a print statement.  I would like to save the values to string and save to a txt file, which I will open and send via MQTT.  Can you describe how to convert the byte pointer variables to characters?
Many thanks,  Jack

Hi.
I think you can use something like this:

String yearString = String((char *) year);

I didn’t test it.
Regards,
Sara

This worked fine.  Big thank you!

I need to work on my cpp.

Great!
I’ll mark this issue as resolved. If you need further help, you just need to open a new question in our forum.
Regards,
Sara