That was the date of episode 3×07 of The 100, where Lexa, one half of Clexa, was killed a minute after finally getting together with her main character love interest. She’d been introduced the previous season and then returned to much fanfare the next, with fans invited to come to the taping of the season finale with her in it. Turns out she’d been killed some episodes before and what appeared in that ep was an AI construct.
Fans carry a LOT of distrust over that, especially since the rest of 2016 seemed to only confirm those feelings of being a target by continuing to kill so many more f/f characters. As shows have slowly started to replenish that lost rep, people are beginning to relax, but I suppose this fandom experience is reminding people of Clexa, a canon f/f fandom this invested and enthusiastic and large.