Light-year is the distance light travels in a year. It is estimated that light crosses interstellar space at 186,000 miles (300,000 kilometers) per second and 5.88 trillion miles (9.46 trillion kilometers) per year. With current technology, it would take us approximately 37,200 years to travel the distance of one light-year. Time dilation means that, for those traveling close to the speed of light, time would slow down to almost nothing.
If a spacecraft were traveling at the speed at which Helios 2 was traveling, it would have taken 4269 light-years to travel one light-year. If a Saturn V rocket that took man to the Moon traveled, it would take 108,867 years to travel one light-year. If you wanted to travel with a constant acceleration of 1G and then a deceleration to the very edge of the observable Universe, it would take an incredibly long time. If a spacecraft traveled at the speed of one light-year per human year, it would take 28,000 years to reach the center of the Milky Way.
However, if you accelerate at that rate for years, you can travel billions of light years during a human lifetime.