configtime function and NTP servers

[kwboi]

Hello.

In my code I setup the NPT servers and time zones/offsets myself and do it just once. However, I've noticed that the Firebase-ESP code also calls the configtime function setting the offset and the NPT servers. Does that mean Firebase-ESP is overwriting my settings? If so, what should I do to keep my settings?

Thank you!

[mobizt]

In ESP32 and ESP8266, your device system time will be used as library reference time then there is no change to your device system time if it is already set otherwise, it will be set from the NTP time.

[mobizt]

There is some exception that your device system time will always be re-synch or set from NTP server when you set config.time_zone to the value was changed from its default value (0).

Note:
The default value of config.time_zone will be changed or updated when the NTP server time synching is completed.

In your case, you should not assign any value to config.time_zone other than 0 to not initiate the internal NTP time synching.

[kwboi]

Hello.
I’ve written code to update the ESP32 internal RTC w/ the date and time from NTP severs. There’s connection to the internet and the RTC gets updated to the correct time provided by one of the NTP servers as expected. Here’s what the code is doing:

1. It calls configTime(0, 0, “pool.ntp.org”, “time.nist.gov”, “time.google.com”) once.
2. It calls sntp_set_sync_interval(60000) once.
3. Then it goes into a loop that calls getLocalTime() and Firebase.ready() functions;
   Although the time and date are correct initially, after about 24 hours I start noticing a drift in the time returned by getLocalTime(), i.e., it no longer matches the current time. It is as if the RTC only got updated once. Any ideas as to why this is happening? Could there be a conflict w/ the FB library?

[mobizt]

That is normal in embedded system.
The system time (based on timer/counter) of mcu is not precision based on its clock frequency.
You need to re-synch your device time via NTP at some interval.

Again, library does not touch the device system time if it once set i.e., time(nullptr) returns the timestamp that is greater than this valid timestamp and leave config.time_zone to be its default (zero).

[mobizt]

I wonder that you already re-sync the time every 60 seconds.

You should assign the sntp synch notification callback as this tutorial to make sure that time was re-synched successfully.

[mobizt]

FYI

If your device woke up from deep sleep, some internal core environment variables are lost included time zone ("TZ").

You should call configTime again, followed by calling the time zone environment setting and initializing functions.

configTime(0, 0, "pool.ntp.org", "time.nist.gov", "time.google.com");
setenv("TZ", "your time zone env variable string e.g., JST-9 for Asia/Tokyo", 1); 
tzset();

For time zone environment variable string, see https://raw.githubusercontent.com/nayarsystems/posix_tz_db/master/zones.csv

https://man7.org/linux/man-pages/man3/setenv.3.html
https://man7.org/linux/man-pages/man3/tzset.3.html