TimeLib.h or NTPClient.h

[gfvalvo]

@brice3010

Is there no limit on the frequency NTP servers may be polled? To prevent flooding etc.?

The servers will throttle you if you start banging them too hard. But, as pointed out, you don't need to:

@noiasca

the ESPs have (some kind of) RTC.
The NTP polling interval is handled in the background.
When you just try to get current time, you get the time from the RTC.
Meaning, a time(&now); // read the current time does not cause a NTP call - it reads the current time from its internal RTC.

I don't use ESP8286 much, but on ESP32, the RTC is more than adequate to go an hour or more between NTP updates.

@brice3010

But what does the text in, for example, CET-1CEST,M3.5.0,M10.5.0/3 mean?

That's a POSIX time zone specification that is used to set the TZ Environment Variable.

The ESP8286 core includes a TZ.h file with lots of predefined time zones. Just do:

#include <TZ.h>

Interestingly, ESP32 doesn't have this. So I just copy the file into my ESP32 environment. Said file is attached herein.
TZ.h (22.2 KB)