Computing Moon Phase in 150 Lines of JavaScript — Julian Date, Synodic Month, and SVG Terminator

📰 Dev.to · SEN LLC

Learn to compute the moon phase in JavaScript using Julian Date and Synodic Month, and visualize it with SVG

intermediate Published 19 May 2026
Action Steps
  1. Calculate the Julian Date using the given formula and JavaScript code
  2. Determine the Synodic Month and its impact on moon phase calculation
  3. Use SVG to visualize the moon phase and terminator
  4. Apply the computed moon phase to a web application or API
  5. Test and refine the code for accuracy and performance
Who Needs to Know This

Developers and data scientists can benefit from this tutorial to create interactive moon phase visualizations, and product managers can use this to enhance user experience in astronomy-related applications

Key Insight

💡 Julian Date and Synodic Month are crucial for accurate moon phase calculation

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Compute moon phase in 150 lines of JS! #astronomy #javascript

Key Takeaways

Learn to compute the moon phase in JavaScript using Julian Date and Synodic Month, and visualize it with SVG

Full Article

"Wait, what phase is the moon in tonight?" — that question deserves a 150-line answer, not a Google...
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