The transition or rollover from one day to the next is at 2 AM EDT, which corresponds to 6 AM UTC. This is when the daily jobs roll over each day. During Standard Time, it's at 1 AM EST = 6 AM UTC. You'll need to adjust that to your local time.

EDIT: Okay, I see you said that the event began at 8 AM in your time zone, which I'm guessing is MDT, since it began at 10 AM EDT. I made myself a little list to help me keep track of when I can expect to earn a particular number of tickets. I'm including a modified version of it below, with the projected daily ticket numbers for you based on what you said.

3rd Q3 Event, starting with 02 tickets
Thu Sep 05, 08 AM - Thu Sep 05, 11:59 PM = 04 tickets
Fri Sep 06, 12 AM - Fri Sep 06, 11:59 PM = 06 tickets
Sat Sep 07, 12 AM - Sat Sep 07, 11:59 PM = 08 tickets
Sun Sep 08, 12 AM - Sun Sep 08, 11:59 PM = 10 tickets * spend them!
Mon Sep 09, 12 AM - Mon Sep 09, 11:59 PM = 02 tickets
Tue Sep 10, 12 AM - Tue Sep 10, 11:59 PM = 04 tickets
Wed Sep 11, 12 AM - Wed Sep 11, 11:59 PM = 06 tickets
Thu Sep 12, 12 AM - Thu Sep 12, 11:59 PM = 08 tickets
Fri Sep 13, 12 AM - Fri Sep 13, 11:59 PM = 10 tickets * spend them!
Sat Sep 14, 12 AM - Sat Sep 14, 11:59 PM = 02 tickets
Sun Sep 15, 12 AM - Sun Sep 15, 11:59 PM = 04 tickets
Mon Sep 16, 12 AM - Mon Sep 16, 09:59 AM = 06 tickets

So you should be able to earn 2 more tickets today, to get to 8.

However, there are three important things you need to be aware of with regard to killing the sewer bosses:

(1) Make sure you kill the right kind of boss, either a patrolling, lamp-carrying boss with flags on its back, or one of the named group bosses at the locations marked by the crossed-swords icon.

(2) Make sure you loot the boss's corpse. I'm not sure if this is necessary with the lamp-carrying boss, but it's definitely necessary with the group bosses, because the tickets are on its corpse along with any other loot.

(3) Apparently, if more than 12 players killed the boss, only 12 players will get looting privileges; for everyone else, the corpse can't be looted. So if you killed a boss but didn't get looting privileges, you'll need to kill it again, until you finally do get looting privileges.

It sounds like you either didn't know you needed to loot the corpse and ran off without looting it, or else you didn't get looting privileges and didn't know you needed to try again.

So hopefully you can try again before midnight tonight and get your 2 tickets for Saturday. But if you kill the boss and there are no tickets on its corpse, maybe you had looting privileges the first time and missed out on those tickets by not looting the corpse? All you can do is try again before midnight and see what happens.

That stinks. Have you tried again anyway?

Good to hear!!! Apparently there was a glitch that kept a lot of people from getting their tickets, hopefully it's been fixed for all now.

This morning I helped kill one of the group bosses in the DC section of the sewers, and apparently the boss did NOT drop any tickets. I'd already earned mine earlier, but people who hadn't did not get tickets from that boss. So we went to kill Gati, who has been dropping tickets reliably, and they DID get their tickets from Gati. So it seems that some group bosses either don't drop tickets at all, or are sometimes buggy about it, while other group bosses drop tickets reliably.

Yup. Gati is my heroine.

This is the first event I've ever had an issue with tickets.
Also, being the first event killing bosses in PvP, I dont understand your comments on tickets working that way before.