Giving the 378.56beta1 a go on my RT-AC68U. After initial installation I noticed it thought CTF+FA NAT acceleration was enabled. When it is in this state, the Traffic Monitor doesn't show data correctly. I did Factory Reset and now just CTF shows and the Traffic Monitor works as far as registering data. I then verified my timezone and DST settings.
There seems to be two clocks in this thing which seems to have been throwing off the Daily Traffic monitoring where it changes the day based on UTC time and not my local time. Time will tell if this firmware does the same. I noticed when I turned on my TV which is connected that this appeared in the log (removed any identifying numbers):
Oct 17 16:48:29 kernel: wl_module_init: passivemode set to 0x0
Oct 17 16:48:29 kernel: wl_module_init: igs set to 0x0
Oct 17 16:48:29 kernel: wl_module_init: txworkq set to 0x1
Oct 17 16:48:29 kernel: eth1: Broadcom BCM4360 802.11 Wireless Controller
Oct 17 16:48:29 kernel: eth2: Broadcom BCM4360 802.11 Wireless Controller
Oct 17 21:49:23 dnsmasq-dhcp[442]: DHCPDISCOVER(br0)
Oct 17 21:49:23 dnsmasq-dhcp[442]: DHCPOFFER(br0)
Oct 17 21:49:23 dnsmasq-dhcp[442]: DHCPREQUEST(br0)
Oct 17 21:49:23 dnsmasq-dhcp[442]: DHCPACK(br0)
You'll notice the time difference of 16:48 and 21:49. Above, the router shows Oct 17 17:15:13 at the moment. Shouldn't the new log entries be based on my local time and not UTC time?
Update: Yep, the Daily Traffic monitor is on the 18th now even though it's only 7:26pm locally:
http://i.imgur.com/WGZwgPt.png