SlipStack is a note-taking app that includes tags, calendar, markdown, attachments, auto-tagging, bookmarking tag selections

Features:

• Hierarchical Tags with Categories
• Multiple Tags Filtering with 'AND', 'OR(calendar)', 'NOT' Operations
• Calendar with Date Filtering
• Multiple Collection Libraries
• Tag Combination Bookmark
• Auto-Tagging when Create a New Article
• Markdown Support
• File Attachment Support

Use Case:

• Diary/Planner
• To-do management
• Note Taking
• Photo/Media Organizer
• Filing/Archiving
• Reference Manager