3rd day of the month of Ilm (Knowledge) 173 B.E.

Interestingly, there was a new calendar, instituted by the Bab (Gate), from Shiraz, Persia, in the historical province of Elam, where Daniel had a vision.
This calendar began on Naw Ruz (New Year) March 21st, 1844.  (Actually, it was after sunset March 20th, but sunset marks the new day.)

The above date was also the 1st day of the 3rd month of the year 1260 AH of the Muslim calendar, 1 Rabi I 1260 AH.

Thus, the year 1260 AH = 1844 AD = ONE BE

The intersection of these three calendars is not coincidental, but rather reflects the ancient prophetic traditions mentioned in the Book of Daniel, as well as Revelation, and provides insight into the connectivity of the Jewish, Christian, and Muslim religions as part of a single process of progressive revelation.

A quick Google search of a Muslim Christian Calendar Converter confirms the numbers of the years mentioned above, and further research into the Baha'i Calendar confirms that as well.