Addition to RTClib by JeeLabs http://news.jeelabs.org/code/ that takes care of Daylight Savings Time (DST) for Europe. https://en.wikipedia.org/wiki/Summer_Time_in_Europe
TL;DR Winter time is considered to be the baseline, and during DST period clock shows time that's 1 hour ahead of baseline.
Designed to be a drop-in replacement for RTClib (when working with RS3231 sensors):
Code with RTClib
#include <RTClib.h>
RTC_DS3231 rtc;Just replace these lines with
#include <RTC_DS3231_DST.h>
RTC_DS3231_DST rtc;and the rest of the may remain untouched.