How this calculator works
Enter speed as fraction of c, proper time (years). CalcStack applies the displayed formula and reports each intermediate planning value with the units shown.
Formula / method
γ = 1 ÷ √(1 − v²/c²); observed time = γ × proper time
Worked example
At 0.8c, one year of proper time corresponds to about 1.667 years for a stationary observer.
Assumptions and limitations
Motion is inertial and speed is constant.
Acceleration, gravity, cosmology and practical travel constraints are not modeled.