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Astronomical Julian Date Calculator

Calculate astronomical julian date with clear inputs, formulas, and supporting results.

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Astronomical Julian Date

Astronomical Julian Date Calculator

Julian Date—
Unix timestamp—
Modified Julian Date—
Results are estimates for informational purposes. Verify critical calculations and project requirements independently.

Calculator Inputs and Outputs

Inputs

  • UTC date — example: 2026-07-28
  • UTC time — example: 12:00

Results

  • Julian Date
  • Unix timestamp
  • Modified Julian Date

Formula used

Julian Date = Unix milliseconds/86,400,000 + 2,440,587.5.

How to Use the Astronomical Julian Date Calculator

Enter the requested values, check the units and assumptions, then select Calculate Astronomical Julian Date. The built-in defaults provide a complete working example.

Formula

Julian Date = Unix milliseconds/86,400,000 + 2,440,587.5.

Understanding the Results

The primary answer appears first. Supporting outputs show related quantities, conversions, dates, costs, ratios, or intermediate values. Calculations keep additional precision before display rounding.

Accuracy Tips

  • Use measured values and consistent units.
  • Review assumptions, rates, timing, and efficiency inputs.
  • Recalculate after changing any condition.

Important Note

This tool provides an informational estimate. Confirm critical financial, medical, construction, scientific, tax, legal, or safety decisions with an appropriately qualified professional.

Calculation Standards

This tool uses documented formulas and high-precision internal values. Displayed results may be rounded for readability. Review the assumptions and verify important decisions with a qualified professional.

Read our calculation methodology