second full moon in a calendar month.
Because there are roughly 29.5 days
between full moons, it is unusual for
two full moons to fit into a 30 or 31
day month (and impossible to fit into
a 28 or 29 day month, so February can
never have a Blue Moon).
The saying "Once in a Blue Moon"
means a rare occurrence, and predates
the current astronomical use of the term,
which seems to be quite recent. In fact,
Blue Moons are not all that rare,
on average there will be one Blue Moon
every 2.5 years. After 1999, the next
Blue Moons will be in November 2001,
July 2004, and June 2007. The last one
before 1999 was in July 1996.
situation which only takes place about four
times a century: two Blue Moons occurring
in the same year. The last time this happened
was in January and April of 1961 and it will
not happen again until January and March of 2018.
A double Blue Moon most commonly occurs in
January/March but is also possible in January/April
or January/May and only when there is no
full moon at all in February. It is also
possible to have a Blue Moon in December of
one year and March of the next year, again,
there is no full moon in the intervening February.
The pictures below were taken on January 31, 1999
6:00 pm
9:30 pm
"Get Windows Media Player" button to download the plug-in
