Hobbyist here, not a programmer/developer/techie, so hope you’ll excuse this submission as an ‘Issue’.

I believe that, like me, other RTClib users get clock inaccuracy with the DS3231. Arduino Forum contributor @gfvalvo helped me to implement its adjustment after a simple addition to RTClib.h. So directly below the section

//
/*!
@brief RTC based on the DS3231 chip connected via I2C and the Wire library
*/
//
(which in the current release 2.1.3 ends with empty line 400), I’ve inserted the following five lines:

// Add Aging Register Access
static constexpr uint8_t agingRegister = 0x10;
int8_t readAging(){
return read_register(agingRegister);
}
void setAging(int8_t newAgingValue) {
write_register(agingRegister, newAgingValue);
}
};
My own sketch already includes the RTClib library and its minimal initialisation

// Initialize the rtc object
rtc.begin();
to which I added the following five lines in setup(), to compensate for my clock’s current slowness.

// Using edited RTClib.h from gfvalvo to adjust AgingRegister
int8_t aging = rtc.readAging();
Serial.println(aging);
int8_t newAging = -50;
rtc.setAging(newAging);
Trial and error will be needed (before hopefully reducing drift to a couple of seconds a week at most), but I already believe it to be working satisfactorily. The method seems significantly simpler than some I’ve seen, so I’d suggest its serious consideration for a future release please.