To decide which system applies to you, you must determine the date that you FIRST entered the military. This date is called the DIEMS (Date of Initial Entry to Military Service) or DIEUS (Date of Initial Entry to Uniformed Services). The date you first entered the military is the first time you enlisted or joined the active or reserves. This date is fixed---it does not change. Departing the military and rejoining does not affect your DIEMS.

Some individuals have unique circumstances that complicate determining their DIEMS. Here are a few examples:

• The DIEMS for Academy graduates who entered the Academy with no prior service is the date they reported to the Academy, not the date they graduated.
• Beginning an ROTC scholarship program or enlisting as a Reserve in the Senior ROTC program sets the DIEMS, not the graduation or commissioning date.
• Members who entered the military, separated, and then rejoined the military have a DIEMS based on entering the first period of military service.
• The DIEMS for members who enlisted under the delayed entry program is when they entered the delayed entry program, not when they initially reported for duty.
• For those who joined the Reserves and later joined the active component, their DIEMS is the date they joined the Reserves.

Be aware that your pay date may be different than your DIEMS. Also, your DIEMS does not determine when you have enough time in the service to retire---it only determines which retirement system applies to you.

Not all Services have their DIEMS dates properly defined in their personnel records. If you have unusual circumstances and are unsure of when your DIEMS date is or believe your records show an incorrect DIEMS date, contact your personnel office to discuss your particular situation.

Now, based upon the date you initially entered the military, you can determine which retirement system applies to you.