An article on Thursday about the arraignment of three men in the
shooting of two New York police officers, one of whom died, misstated
the schedule set by a judge for a trial in the case. The trial is
expected to begin by February, not by “Feb. 30.” The error occurred
when an editor saw the symbol “— 30 —” typed at the bottom of the
reporter’s article and combined it with the last word, “February.” It
is actually a notation that journalists have used through the years to
denote the end of an article. Although many no longer use it or even
know what it means, some journalists continue to debate its origin. A
popular theory is that it was a sign-off code developed by telegraph
operators. Another tale is that reporters began signing their articles
with “30” to demand a living wage of $30 per week. Most dictionaries
still include the symbol in the definition of thirty, noting that it
means “conclusion” or “end of a news story.” Link