THE SPECIFICS OF THE ADAM-GOD TEACHING
Wikipedia gives the following information regarding the specifics of the Adam-God doctrine in [this article]:1
Brigham Young's 1852 announcement
...the first recorded explanation of the doctrine was by Brigham Young, who first taught the Adam–God doctrine at the church's spring General Conference on April 9, 1852. This sermon was recorded stenographically by George D. Watt, Young's private secretary, who was an expert in Pitman shorthand. Watt published the sermon in 1854 in the British periodical Journal of Discourses, in a volume endorsed by Young and the church's First Presidency.
In Watt's transcript of the sermon, Young said he intended to discuss "who it was that begat the Son of the Virgin Mary", a subject which he said "has remained a mystery in this kingdom up to this day". The transcript reads:
"When our father Adam came into the garden of Eden, he came into it
with a celestial body, and brought Eve, one of his wives, with him. He
helped to make and organize this world. He is MICHAEL, the Archangel,
the ANCIENT OF DAYS! about whom holy men have written and spoken—He is
our FATHER and our GOD, and the only God with whom WE have to do.
Every man upon the earth, professing Christians or non-professing,
must hear it, and will know it sooner or later.
Further development by Young
In a special conference on August 28, 1852, Young explained in greater detail the mechanism by which celestial beings like Adam and Eve could give birth to mortal offspring. According to Young, when a couple first become gods and goddesses, they first begin to create spiritual offspring. Then, they begin creating "mortal tabernacles" in which those spirits can dwell, by going to a newly-created world, where they:
"eat and drink of the fruits of the corporal world, until this grosser
matter is diffused sufficiently through their celestial bodies, to
enable them according to the established laws to produce mortal
tabernacles for their spiritual children" (Young 1852b, p. 13). This
is what Adam and Eve did, Young said, and "Adam is my Father (Young
1852b, p. 13).
On February 19, 1854, he reiterated the doctrine in a sermon. He also reiterated the doctrine at the October 1854 General Conference, in a sermon that was reported to have "held the vast audience as it were spellbound" In the October conference, Young is reported as clarifying that Adam and Eve were "natural father and mother of every spirit that comes to this planet, or that receives tabernacles on this planet, consequently we are brother and sisters, and that Adam was God, our Eternal Father."
When Young discussed the doctrine again in early 1857, he emphasized again that "to become acquainted with our Father and our God" was "one of the first principles of the doctrine of salvation", and that "no man can enjoy or be prepared for eternal life without that knowledge". Nevertheless, he said:
"Whether Adam is the personage that we should consider Our Heavenly
Father, or not, is considerable of a mystery to a good many. I do not
care for one moment how that is; it is no matter whether we are to
consider Him our God, or whether His Father, or his Grandfather, for
in either case we are of one species of one family and Jesus Christ is
also of our species.". Young continued... "How much unbelief
exists in the minds of the Latter-day Saints in regard to one
particular doctrine which is revealed to them, and which God revealed
to me -- namely that Adam is our father and God...Our Father Adam is
the man who stands at the gate and holds the keys of everlasting life
and salvation to all his children who have or ever will come upon the
earth" (Sermon delivered on June 8, 1873. Printed in the Deseret
Weekly News, June 18, 1873.)
Just before his death, Young took steps to ensure that the Adam–God theory was taught in LDS temples as part of the Endowment ceremony.
This time period appears to be about 25 years, then.
Today, the LDS Church does not hold to this doctrine in any fashion.