pened between the 1st of January
and the 1st of the following July, the sum of the Olympic year and of
the year before Christ is always equal to 776. The year of the era,
therefore, will be found by subtracting the number of the Olympic year
from 776. For example, Varro refers the foundation of Rome to the 21st
of April of the third year of the sixth Olympiad, and it is required
to find the year before our era. Since five Olympic periods have
elapsed, the third year of the sixth Olympiad is 5 X 4 + 3 = 23;
therefore, subtracting 23 from 776, we have 753, which is the year
before Christ to which the foundation of Rome is referred by Varro.

_2nd._ When the event took place between the summer solstice and the
1st of January following, the sum of the Olympic year and of the year
before Christ is equal to 777. The difference, therefore, between 777
and the year in one of the dates will give the year in the other date.
Thus, the moon was eclipsed on the 27th of August, a little before
midnight, in the year 413 before our era; and it is required to find
the corresponding year in the Olympic era. Subtract 413 from 777, the
remainder is 364; and 364 divided by four gives 91 without a
remainder; consequently the eclipse happened in the fourth year of the
ninety-first Olympiad, which is the date to which it is referred by
Thucydides.

If the year is after Christ, and the event took place in one of the
first six months of the Olympic year, that is to say, between July and
January, we must subtract 776 from the number of the Olympic year to
find the corresponding year of our era; but if it took place in one of
the last six months of the Olympic year, or between January and July,
we must deduct 777. The computation by Olympiads seldom occurs in
historical records after the middle of the 5th century of our era.

The names of the months were different in the different Grecian
states. The Attic months, of which we possess the most certain
knowledge, were named as follows:--

Hecatombaeon. Gamelion.
Metageitnion. Anthesterion.
Boedromion. Elaphebolion.
Pyanepsion. Munychion.
Maemacterion. Thargelion.
Poseideon. Scirophorion.

_Era of the Foundation of Rome._--After the Olympiads, the era most
frequently met with in ancient history is that of the foundation of
Rome, which is the chronolog