Super simple and short code to estimate how long would it take to that far-away star from the perspective of someone inside a ship which moves at 1g according to special relativity.
The calculation assumes you accelerate at 1g half the way, then you deaccelerate at -1g the second half of the trip. Of course this is only the time it takes for a one-way trip.
Simply do:
python howlong.py
Enter the distance to the star you want to visit and that's it!