RPi4 Bullseye Cannot retain rtc-ds3231 hwclock value when internet is OFF

Question

I followed all instructions from Adafruit website but the system clock is still not set after I turn off the internet.

**The clock resets to 2000-01-01 00:00:00 when I turn off internet, shutdown, wait for 5 mins, and reopen rpi. I've been trying to fix this for a week now. Any help will be greatly appreciated. **

cat /etc/os-release

PRETTY_NAME="Raspbian GNU/Linux 11 (bullseye)"
NAME="Raspbian GNU/Linux"
VERSION_ID="11"
VERSION="11 (bullseye)"
VERSION_CODENAME=bullseye
ID=raspbian
ID_LIKE=debian
HOME_URL="http://www.raspbian.org/"
SUPPORT_URL="http://www.raspbian.org/RaspbianForums"
BUG_REPORT_URL="http://www.raspbian.org/RaspbianBugs"

sudo apt-get update

sudo apt-get upgrade

sudo nano /boot/config.txt

dtparam=i2c_arm=on
dtparam=spi=on
dtoverlay=i2c-rtc,ds3231

sudo i2cdetect -y 1

     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:                         -- -- -- -- -- -- -- -- 
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
20: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 
60: -- -- -- -- -- -- -- -- UU -- -- -- -- -- -- -- 
70: -- -- -- -- -- -- -- --   

sudo apt-get -y remove fake-hwclock

sudo update-rc.d -f fake-hwclock remove

sudo systemctl disable fake-hwclock

sudo nano /lib/udev/hwclock-set

#!/bin/sh
# Reset the System Clock to UTC if the hardware clock from which it
# was copied by the kernel was in localtime.

dev=$1

#if [ -e /run/systemd/system ] ; then
#    exit 0
#fi

#/sbin/hwclock --rtc=$dev --systz
/sbin/hwclock --rtc=$dev --hctosys

(WITH INTERNET)

date

Saturday, 18 March, 2023 01:48:29 AM PST

sudo hwclock -w

sudo hwclock -r

2023-03-18 01:48:33.448713+08:00

timedatectl

               Local time: Sat 2023-03-18 01:50:16 PST
           Universal time: Fri 2023-03-17 17:50:16 UTC
                 RTC time: Fri 2023-03-17 17:50:16
                Time zone: Asia/Manila (PST, +0800)
System clock synchronized: yes
              NTP service: active
          RTC in local TZ: no

dmesg | grep rtc

[    9.395322] vc4-drm gpu: bound fe206000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.398153] vc4-drm gpu: bound fe207000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.398838] vc4-drm gpu: bound fe20a000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.400108] vc4-drm gpu: bound fe216000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.400820] vc4-drm gpu: bound fec12000.pixelvalve (ops vc4_crtc_ops [vc4])
[   10.793556] rtc-ds1307 1-0068: registered as rtc0
[   10.797266] rtc-ds1307 1-0068: setting system clock to 2000-01-01T00:13:09 UTC (946685589)

(WITHOUT INTERNET)

pi@raspberrypi:~ $ date
Saturday, 01 January, 2000 08:00:49 AM PST
pi@raspberrypi:~ $ sudo hwclock -r
2000-01-01 08:00:56.567891+08:00
pi@raspberrypi:~ $ timedatectl
               Local time: Sat 2000-01-01 08:01:04 PST
           Universal time: Sat 2000-01-01 00:01:04 UTC
                 RTC time: Sat 2000-01-01 00:01:04
                Time zone: Asia/Manila (PST, +0800)
System clock synchronized: no
              NTP service: active
          RTC in local TZ: no
pi@raspberrypi:~ $ dmesg | grep rtc
[    8.691900] rtc-ds1307 1-0068: SET TIME!
[    8.717235] rtc-ds1307 1-0068: registered as rtc0
[    8.723796] rtc-ds1307 1-0068: setting system clock to 2000-01-01T00:00:21 UTC (946684821)
[    9.111707] vc4-drm gpu: bound fe206000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.112320] vc4-drm gpu: bound fe207000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.112883] vc4-drm gpu: bound fe20a000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.113234] vc4-drm gpu: bound fe216000.pixelvalve (ops vc4_crtc_ops [vc4])
[    9.113702] vc4-drm gpu: bound fec12000.pixelvalve (ops vc4_crtc_ops [vc4])
pi@raspberrypi:~ $ 

Answer 1

Your fundamental problem is turning off fake-hwclock . If the RTC is working it does no harm. Turn it back on.

See https://raspberrypi.stackexchange.com/a/104139/8697

It is unclear if you added any other code but the ONLY thing you need is the appropriate dtoverlay dtoverlay=i2c-rtc,ds3231
(which you can also enable on the fly with sudo dtoverlay i2c-rtc ds3231)

You may need to initially set RTC but normally this happens automatically.

---

sudo hwclock -rv will display details of your RTC; the current time & when last synchronised.

You need to ensure that the RTC is working and the battery is OK. Some RTC use a supercapacitor for backup which are less reliable.

sudo systemctl status fake-hwclock will tell you its status.