How can I find the time a floating IP was associated or disassociated from an instance?

If you need to find the date/time a floating IP address was associated or disassociated from an instance, you can open a support ticket and ask that we check the auth log on the hypervisor where your instance is located. The log entry will look similar to:

Oct 14 23:24:59 hypervisor-name sudo: neutron ... neutron-rootwrap /etc/neutron/rootwrap.conf
ip netns exec qrouter-tea045f7-6a1c-4687-8a5e-ffecd51b2bcf ip -4 addr del 179.147.93.21/32 ...