I speak about the drift at What will happen to the calendar if the Sanhedrin is re-instituted
Calendrical Calculations 3rd Edition by Nachum Dershowitz (Author), Edward M. Reingold (Author) gives the algorithms for a number of calendars using Lisp. The fixed calendar of Hillel II is one of the algorithms presented.
The Jewish Encyclopedia states that Hillel II instituted the fixed calendar officilly in the year 4119 (359 CE). However, it also states that the Sanhedrin had been using it for the previous generation.
As @Scimonster said, Date Converter will give the translation from the year 3761 (1 CE) to 13760 (9999 CE)
Note that even though the Gregorian calendar was not instituted until October 1582, the site appears to use the Gregorian calculation only. This means that the Julian calendar used before that will diverge the farther back that the calculation is taken.
The Jewish Calendar: An Overview states that
In the fourth century, Hillel II established a fixed calendar based on
mathematical and astronomical calculations.
CALENDAR, HISTORY OF states
Under the patriarchate of Rabbi Judah III. (300-330) the testimony of
the witnesses with regard to the appearance of the new moon was
received as a mere formality, the settlement of the day depending
entirely on calculation.
The persecutions under Constantius finally decided the patriarch,
Hillel II. (330-365), to publish rules for the computation of the
calendar, which had hitherto been regarded as a secret science. The
political difficulties attendant upon the meetings of the Sanhedrin
became so numerous in this period, and the consequent uncertainty of
the feast-days was so great, that R. Huna b. Abin made known the
following secret of the calendar to Raba in Babylonia: Whenever it
becomes apparent that the winter will last till the 16th of Nisan,
make the year a leap-year without hesitation.
Later Jewish writers agree that the calendar was fixed by Hillel II.
in the year 670 of the Seleucidan era; that is, 4119 A.M. or 359 C.E.
Some, however, as Isaac Israeli, have fixed the date as late as 500.
Saadia afterward formulated calendar rules, after having disputed the
correctness of the calendar established by the Karaites. That there is
a slight error in the Jewish calendar — due to inaccuracies in the
length of both the lunar and the solar years upon which it is
based — has been asserted by a number of writers.