Once in a Blue Moon

Blue moon is the second full moon in a month that occurs roughly every two and a half years. But don’t expect it to be blue — the name has nothing to do with the color of our closest celestial neighbor! However, New Year’s Eve blue moons are rarer, occurring every 19 years. The last time was in 1990; the next one won’t come again until 2028. will be visible in the United States, Canada, Europe, South America and Africa. For party goers in Australia and Asia, the full moon does not show up until New Year’s Day, making January a blue moon month for them.

The 29.5-day lunar cycle matches up almost perfectly with the 28 to 31 day length of calendar months. Occasionally, however, the one-to-one correspondence breaks down when two full Moons squeeze into a single month. Dec. 2009 is such a month. The first full Moon appeared on Dec. 2nd; the second, a "Blue Moon," will come on Dec. 31st.

Thus the saying: "It only happens once in a Blue Moon."

- Rehel Hasnain Zaidi