OOPS! Ignore me. What I didn't pick up on was my critical mistake.
The time for it
to reach this velocity (0.5c) is given by this equation:
t = v/a = 1.5×108/10 = 3.06×107 s = 174 days
ie: what they were saying was that the time taken to reach v= 0.5c was 174 days, NOT the time for the entire trip
Sorry!
Stuart