Digital clock gains time

Question

I have a Wextclox model 66713, 1.5" red LED alarm clock with the translucent plastic case, that gains about 5 minutes every 8 hours. The manufacture date on the bottom is 5-99! I love this clock, and would really like to keep it going. The closest thing I can find is the Westclox Triad with 2" numbers. Can this be repaired?