The letter notes they will be dismissed from their jobs as of that date, as well.
There will be exceptions -- for instance, when the student was sent abroad under an interstate agreement.
The letter of notification implements a general decree passed by the Education Ministry in June 2003.
In a televised speech last year, Turkmen President Saparmurat Niyazov explained the motives behind the decree.
It is unclear why the year 1993 was chosen, or how many people are affected by the decree. But the dismissal of teachers, doctors, engineers, and other professionals in Turkmenistan's state-run economy is expected to be massive.
Observers say the move will further erode the country's social services, increase unemployment, and force many members of Turkmenistan's educated class into permanent exile.
Aaron Rhodes, the executive director of the International Helsinki Federation for Human Rights in Vienna, called the move "one more step in the direction of isolation and mediocrity in Turkmenistan. It's another attack on the future of Turkmenistan as a member of the international community, and it doesn't bode very well for the ability of the Turkmen people to solve their own problems."
Rhodes sees the decree as part of a broader effort by authorities to filter foreign influence out of Turkmen society and to exert more control over citizens.
An unidentified resident of the capital Ashgabat agreed. "It seems it is appreciated if fewer people move abroad," he told RFE/RL. "If they travel less, they will get less information. It may be done to block the development of the youth's worldview."
However, he added that he does not believe the purpose of the measure is to abuse minority rights. "If minorities have an education, they could move to other countries and could find jobs there," he said. "Most of them are going to move if they can."
Bess Brown, a Germany-based expert on Central Asia, says the new measure is consistent with past government practices.
"Obviously, most people affected by it were going to be people who had taken degrees in the Russian Federation because that's where people went to study, including Niyazov," Brown said. "His degree is from Leningrad [Polytechnic Institute]. [But] it affects everyone of every nationality. It's part of this policy of wrecking the educational system that Niyazov has been engaged in for several years now."
Turkmenistan's education system has been in steady decline. Universities accept only about 3,000 students a year, one-tenth of the number before independence in 1991.
Education levels are far below international standards, as well, making it more difficult for students to transfer credits to foreign universities.
Professors and students who do not have a thorough command of the Turkmen language are also being pushed out of the country's universities, which now teach almost exclusively in Turkmen.
(Naz Nazar, director of RFE/RL's Turkmen Service, contributed to this report.)