One formula · your inputs
Unix time to Julian date converter
Unix time counts seconds from 1970-01-01 00:00:00 UTC, while the Julian Date relation places that instant at JD 2440587.5.
The converter applies the arithmetic offset and also subtracts 2400000.5 for Modified Julian Date.
Formula
How it is calculated
JD = Unix seconds ÷ 86400 + 2440587.5; MJD = JD − 2400000.5- Use a timestamp expressed in seconds, not milliseconds.
- Divide it by 86,400 seconds per day.
- Add the Unix-epoch Julian offset, then derive MJD.
What the result represents
A linear conversion between two time-number origins.
The page keeps every decision-bearing quantity visible as an input. It does not look up a product catalogue, current market value or hidden recommended preset.
Limits of the model
This arithmetic does not model leap seconds, alternate time scales such as TT or TDB, calendar reform, or uncertainty in the supplied timestamp.
Use the number to compare transparent scenarios. Verify critical observations, equipment combinations and coordinates independently.
Questions about this calculation
Does this time-coordinate calculator choose equipment for me?
No. It evaluates only the displayed formula with the numbers you enter and does not make a purchase, compatibility or safety decision.
Why can the observed result differ?
Real optics and observing conditions add obstructions, transmission losses, aberrations, seeing, focus and measurement uncertainty that are outside the arithmetic model.
Can I use the result for navigation or safety-critical work?
No. SkyClock tools are transparent planning estimates, not certified navigation, engineering or safety instruments.
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