A comprehensive campaign calendar should include: 1. Send Dates: The specific dates and times when emails will be sent. 2. Campaign Objectives: Clear goals for each campaign. 3. Target Audience: Segments of your email list that will receive the emails. 4. Content Themes: The main topics or promotions for each email. 5. Metrics to Track: KPIs such as open rates, click-through rates, and conversions.