This has been an issue since they messed up AQ and had to delay it a day a few weeks ago. The missing event will occur tomorrow along with the normal first day of AQ event so there will be 2 1 day events. They still should fix it because who knows what other issues it could cause or interact with down the line but despite many other posts about this previously Kabam has not responded or acknowledged it.
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https://forums.playcontestofchampions.com/en/discussion/303372/1-day-event-missing