Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
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for the purposes of our monthly and yearly subscriptions , a month constitutes 30 calendar days , a year constitutes 365 calendar days and two years constitutes 730 calendar days . 

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. OPTIONS: ["Arbitration", "Choice of law", "Contract by using", "Jurisdiction", "Unilateral termination", "Content removal", "Limitation of liability", "Unilateral change", "None"].