[timeattack]

You can't change time in container, but it's possible to change timezone files.

With generating fake timezones it is possible to change time in container.

[cyphar]

This doesn't change what gettimeofday(2) gives you (and actually you can't even use ptrace easily to fake the time of day because gettimeofday(2) isn't a real syscall -- it's actually implemented as a read from the vDSO page the kernel maps into every process).