You can receive SSD benefits retroactive to one year from the date you filed your application, if you were disabled back to that time. However, the 5 month waiting period still applies. SSI benefits are only payable from the date you filed your application.
Example: Alex became disabled on June 13, 1994. She filed an application for SSD and SSI benefits on June 13, 1995. She was awarded benefits on January 1, 1996. Alex's SSD benefits would be retroactive to June 13, 1994, but the first month that SSD benefits would be payable to her would be December 1994. SSI benefits would begin on June 13, 1995, the date of her application.