Answer from Hohmannfan is accurate, but also please note:
a) That calculation require instant acceleration to 0.5c to apply. And since we talk for 'hard science fiction', such thing is quite... embarrassing at least. You have to use a different formula/calculator to calculate time needed based at some acceleration - unless you decide that your starship accelerates (and decelerates!) to 0.5c at no considerable time. 0.5c is about 150 million meters per second(!) so hypothetical thrusters that are capable of get that velocity starting from 0 m/sec at, lets say, 1 day or even 1 month only, are highly likely to also get you to even higher velocities. If, on the other hand, you assume e.g. 1 year accelerating and 1 decelerating, something also 'too much' but definitely more 'realistic', you need 2 years + the above formula for all distance minus the distance traveled while accelerating and decelerating.
b) When it comes to relativistic time, calculations are easy but what that exactly means for 2 different frames of reference is extremely hard for the average mind to comprehend, if both frames have humans. See the larger scale: A proton takes 100.000 years to cross the galaxy for us to observe(from earth frame of reference), but only takes 296 seconds for the proton itself(own frame of reference).
So for a go and return, 17*2=34 years have passed for earth observant and 14.7*2=29.4 for the traveler. 4.6 years difference or 'difference feeling'. This does not necessarily means that travelers are 4.6 years younger biologically.
Extra info: Lots of comments so i clarify some things to help the writer:
First, to clear again my position, i add 2 things:
Acceleration and deceleration time should be considered, it makes it closer to hard fiction
Time dilation is not experimentally proven that affects aging of humans, and that means that it is a small window for the writer that actually helps.
Now about time dilation and how much time has been elapsed for different frames of reference: The static earth based frame of reference needs more time to get information that has happened. Imagine it as a network lag or latency. The starship will get time X to get to destination no matter what. This time X is X for the staship, for everyone in the starship, and for an observer travelling next to the starship and has a nice external view all the way. For an observer on earth, since the starship is constantly moving AWAY, it will take more and more time for the INFORMATION, the light the ship sends back, to reach earth. This means what you see from earth at any given time is the past position of the ship. The ship is really much far away than you see, again at any time. That is why it takes 'more time' for earth, the ship eventually reach destination at time X, but earth observer at time X will see the ship still going, and reach destination at X+Y, where Y is the time the light showing the ship in orbit takes to go back in earth.
To change the scale may help: Changing speed: If the ship exceeds the speed of light it will simply disappear from view from earth, because at any given time, the light the ship emits to earth travels AWAY from earth, as simple as that.
Changing journey distance: The ship goes to another galaxy. The distances are impossible to comprehend but if the ship goes with 05.c all the way the time difference between the arrival of the ship and when earth sees that arrival will be the actual travel time plus the time light needs to reach us from that galaxy. That is, the ship will reach at some time X and we know it X+some millions of years later, e;g; 12 for those we have observed at galaxies within 3.8 megaparsecs.
And a final example: When ship reach destination, enter a fantastic wormhole and INSTANTLY is placed at earth orbit, happily observe itself travelling to destination and enter the wormhole!