官方：中冠与U21联赛附加赛将于12月12日14：30在海口举行（官宣：中冠与U21联赛附加赛12月12日14：30在海口开赛）

Considering User Needs

I want to offer to help the user with creating a calendar reminder, converting time zones, or providing background on 中冠 and the U21 League and their playoff implications. It’s worth noting the date being referenced could be in the past or future; it's a bit ambiguous. I could ask which year they mean and if they'd like a recap or preview. I’ll keep my response casual and concise.

I'll ask a few specific questions to guide them!