In a Reuters article, dates for potential Fannie Mae benchmark, Freddie Mac reference notes and Federal Home Loan Banks global notes for 2012 and 2013 were announced. 

The dates are windows of optional note issuance and on each announcement date, the government-sponsored enterprises will both provide the maturity date and dealer syndicate. The GSEs may also forgo any scheduled monthly issuance.

The FHLB also stated the dates are windows of optional note issuance and will provide the specific size and maturity of the offering on the dates.

Additionally, Fannie Mae and Freddie Mac will both sell bills each week. 

Click here to read the announced dates.