This library uses a DS3231 RTC as a replacement for ESP32 NTP client, including time zone, for complete off-line time keeping.

This library provides web pages to set date/time and time zone, via either an ESP32 Access Point or the local network.

User code just uses the standard ESP32 time/date methods and does not have access the RTC.
The library keeps the ESP32 system time synced to the RTC to within +/-5ms.

Includes examples of optional syncing of RTC from NTP and of using AsyncWebServer instead of the basic ESP32 webserver.

This RTC_NTP_replacement library is for the ESP32 and DS3231 RTC and has the following features:-
– Runs completely off-line, using the RTC (DS3231) to synchronize the ESP32's system clock to within a few milliseconds.
– Uses the standard ESP32 time methods to get times and dates. The RTC is not accessed from user code.
– Provides 'smooth' synchronization of the ESP32's system clock to the RTC's time for consistent time stamps.
– Provides locally served web pages to set the time and the time zone. The web pages are formatted for easy display on a mobile phone.
– Has a time zone parser to clean up the user inputted time zone to a valid one that the ESP32 can use.
– Can optionally to use an NTP server to synchronize the RTC's date and time which then synchronizes the system time.
– Can optionally to use AsyncWebServer instead of ESP32's built in web server

See RTC_NTP_replacement Tutorial

V1.0.4 intial NTP request is compensated for delays in setup()
V1.0.3 increased NTP request interval to 1h (was 1min)
V1.0.2 renamed webpages.cpp/.h to RTC_webpages.cpp/.h
V1.0.0 initial release