Ok, I had my acronyms wrong... Yes, BASD is the date that begins your active federal service and for Academy Grads is the day you are commissioned. However, your retirement plan is based on your DIEMS date and it is still R day.
Per Army HR Command: The Date of Initial Entry into Military Service (DIEMS) is the date an individual was initially enlisted, inducted, or appointed in a regular or reserve component of a uniformed service as a commissioned officer, warrant officer, or enlisted member. Breaks in service do not affect a DIEMS date. Military Academy cadets (date of entry into the academy), ROTC cadets (date of scholarship contract or date the cadet began the advanced ROTC course, whichever is earlier) and members of the delayed entry program (Date enlistment contract signed, regardless of when the Soldier entered active duty.) are considered under these provisions. The DIEMS is the initial contract signed via the Soldier; obligating the Soldier to any type of military service, even if it was later voided and determines which of the retired pay formulas a Soldier is eligible to utilize upon retirement. The DIEMS date is utilized to determine the length of service and associated benefits. DOD 7000.14-R Financial Management Regulation, Volume B, chapter 1, paragraph 010102A states the Date of Initial Entry into Military Service (DIEMS) determines whether the retired pay base is the monthly basic pay of the member before retirement or an average of the highest 36 months of basic pay applicable during the member's career.