The event ended like maybe a few minutes after the quests became unable to turn in. I’m surprised how fast it happened, given usually the chest events tend to linger a bit longer before they finally get switched off.
Unfortunately, I was a bit too lazy to turn in my snowballs before when the cutoff was stated to be, and was banking on them being a little late on the switch so I could squeeze in a few more dungeons. I didn’t have enough to turn in for the quiver anyways, but RIP bagston skin.