Qual preposição usar quando digo apenas mês e ano?

At = para uma hr precisa (at 10 o´clock, at dinnertime, at midnight...)
In = para os meses, anos, séculos, períodos longos (in June, in 2001, in the next century...)
On = para dias e datas específicas (on Friday, on 25 Dec., on my birthday, on New´s year Eve...)

* Penso que a preposição IN neste caso, seria a mais indicada justamente porque não há referência de uma data específica, embora o ano tenha sido mencionado.

To "special days[/u]"[/i], (aka, day in wich someone´s born) we use the preposition on.



http://www.chiangraitimes.com/wp-conten ... -time2.jpg

http://www.biography.com/people/groups/born-on-march-03



Learn more about people born on a given day on our birthday horoscope pages. You can enjoy today's birthday horoscope or look up a horoscope for any particular date by navigating below to the month and then date.
http://www.famousbirthdays.com/horoscope/







Being a Scorpio born on November 14th, your caring and sensitive nature is matched by tremendous willpower and determination...yada yada, blah blah blah etcetera etcetera etcetera and on an on and on....

http://www.famousbirthdays.com/horoscop ... ber14.html

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To a "time of the year" (aka, month-year; so, specific day is not involved.) we use the preposition IN.

in January, 1968.
(Oxford examples, see the following link, please) on page 14.
http://pt.slideshare.net/ebrammer/79-pr ... ime-images