Hindus celebrate the sathabhishekam in their 81st year, but they are mathematically challenged. Since you basically witness 12 moon orbits a year, 80 clocks up only 960 moon orbits. As per the traditional calendar, there is an adhika-maasa (also called mala-maasa, or intercalary month) about every 2.5 years. So in 80 years, there would be about 32 adhika-maasas. The remaining 8 new moons are seen in the 81st year.
You can actually count 1,000 new moons. Let me state it differently: The synodic period of the moon is about 29.5 days. So, it takes about 80.82 years for 1,000 synodic lunar months to be completed.