usage AKETIME="@2000-01-01 11:12:13" not working well

[nameissoso]

user1@user1:$ docker run --name time_test13 -it -d
-v /home/user1/libfaketime/faketime/:/usr/local/lib/faketime
-e LD_PRELOAD=/usr/local/lib/faketime/libfaketime.so.1
-e FAKETIME_DONT_RESET=1
-e FAKETIME_NO_CACHE=1
-e FAKETIME="+100d"
ubuntu:24.04
bash -c "tail -f /dev/null"
f3f22367843404ba2eea2978ae843cffa46ad7abfa07c7193d2d63ae48244989
user1@user1:$ docker exec -it time_test13 /bin/date
Fri Nov 28 01:33:33 UTC 2025
user1@user1:$ docker exec -it time_test13 /bin/date
Fri Nov 28 01:33:35 UTC 2025
user1@user1:$ docker exec -it time_test13 /bin/date
Fri Nov 28 01:33:37 UTC 2025
user1@user1:$ docker run --name time_test14 -it -d
-v /home/user1/libfaketime/faketime/:/usr/local/lib/faketime
-e LD_PRELOAD=/usr/local/lib/faketime/libfaketime.so.1
-e FAKETIME_DONT_RESET=1
-e FAKETIME_NO_CACHE=1
-e FAKETIME="@2000-01-01 11:12:13"
ubuntu:24.04
bash -c "tail -f /dev/null"
2dad6afb4395f11e35b42901bfbc3df63c37c541678ced4894ea47da947bc15a
user1@user1:$ docker exec -it time_test14 /bin/date
Sat Jan 1 11:12:13 UTC 2000
user1@user1:$ docker exec -it time_test14 /bin/date
Sat Jan 1 11:12:13 UTC 2000
user1@user1:$ docker exec -it time_test14 /bin/date
Sat Jan 1 11:12:13 UTC 2000
user1@user1:~$ docker exec -it time_test14 /bin/date

The above is my example,Why while I usage FAKETIME="@2000-01-01 11:12:13", The time does not change anyway.

[SubOptimal]

@nameissoso It works as expected.

From the man page

Start-at timestamps: "@YYYY-MM-DD hh:mm:ss"
     The wall clock will start counting at the given timestamp for the program. This can be used for specifying ab‐
     solute timestamps without freezing the clock.

Which means FAKETIME specifies the start time for a given program, and with FAKETIME_DONT_RESET=1 the time will increment for all new child-processes.

When you run docker exec -it time_test14 /bin/date each date is executed as child of a new bash. The bash is the program for which the clock will start counting. Also to note: date is not executed as child of the bash process from the deamonized docker run.

Without a container, it would be similar to following script

!/bin/bash

export LD_PRELOAD=/usr/local/lib/faketime/libfaketime.so.1
export FAKETIME_DONT_RESET=1
export FAKETIME_NO_CACHE=1
export FAKETIME="@2000-01-01 11:12:13"

echo "[*] first date"
bash -c date
sleep 2
echo "[*] sedond date"
bash -c date
sleep 2

As for each date the clock starts again from the specified date, they print the same date time.

[*] first date
Sat  1 Jan 11:12:13 CET 2000
[*] sedond date
Sat  1 Jan 11:12:13 CET 2000

Whereas if you run the following script

#!/bin/bash

export LD_PRELOAD=/usr/local/lib/faketime/libfaketime.so.1
export FAKETIME_DONT_RESET=1
export FAKETIME_NO_CACHE=1
export FAKETIME="@2000-01-01 11:12:13"

echo "[*] third and fourth date"
bash -c "date;sleep 2;date"

Each date is executed as a child process of the same bash, so the clock will increment for the child-processes.

[*] third and fourth date
Sat  1 Jan 11:12:13 CET 2000
Sat  1 Jan 11:12:15 CET 2000