Is blacklist enabled 24hrs?

If the Network Services Filter blacklist is enabled from 00:00 to 23:59 (the default) will it also work in that last minute to midnight, from 23:59 to 0:00? Or can I expect a problem with it failing? How do we get it to block devices from WAN 24/7 without failing?

Thanks if anyone can clarify,

Cheers!

Using Merlin version 384.5