g the succession of events. For, since the commencement of the
era is placed at an intermediate period of history, we are compelled to
resort to a double manner of reckoning, backward as well as forward.
Some ambiguity is also occasioned by the want of uniformity in the
method of numbering the preceding years. Astronomers denote the year
which preceded the first of our era by 0, and the year previous to that
by 1 B.C.; but chronologers, in conformity with common notions, call the
year preceding the era 1 B.C., the previous year 2 B.C., and so on. By
reckoning in this manner, there is an interruption in the regular
succession of the numbers; and in the years preceding the era, the leap
years, instead of falling on the fourth, eighth, twelfth, &c., fall, or
ought to fall, on the first, fifth, ninth, &c.

In the chronicles of the middle ages much uncertainty frequently arises
respecting dates on account of the different epochs assumed for the
beginning of the Christian year. Dionysius, the author of the era,
adopted the day of the Annunciation, or the 25th of March, which
preceded the birth of Christ by nine months, as the commencement of the
first year of the era. This epoch therefore precedes that of the vulgar
era by nine months and seven days. This manner of dating was followed in
some of the Italian states, and continued to be used at Pisa even down
to the year 1745. It was also adopted in some of the Papal bulls; and
there are proofs of its having been employed in France about the middle
of the 11th century. Some chroniclers, who adhere to the day of the
Annunciation as the commencement of the year, reckon from the 25th of
March following our epoch, as the Florentines in the 10th century.
Gregory of Tours, and some writers of the 6th and 7th centuries, make
the year begin sometimes with the 1st of March, and sometimes with the
1st of January. In France, under the third race of kings, it was usual
to begin the year with Easter; and this practice continued at least till
the middle of the 16th century, for an edict was issued by Charles IX.
in the month of January 1663, ordaining that the beginning of the year
should thenceforth be considered as taking place on the 1st of January.
An instance is given, in _L'Art de verifier les dates_, of a date in
which the year is reckoned from the 18th of March; but it is probable
that this refers to the astronomical year, and that the 18th of March
was taken for the day of the vernal