Your DIEMS date — the Date of Initial Entry to Military Service — is the first day you signed any military obligation, and it permanently locks your military retirement into one of four systems set by federal law. That single day follows you for your entire career. It doesn’t reset if you switch branches, take a break in service, or move between active and reserve components. Because a wrong DIEMS date can push you into the wrong retirement plan and cost you thousands of dollars a year, verifying it is one of the highest-value administrative checks you can do.
What Counts as Your DIEMS Date
Your DIEMS date captures the very first moment you took on a military obligation. Signing a Delayed Entry Program contract counts. Enrolling in a service academy counts. Starting an ROTC scholarship agreement counts. It doesn’t matter that you didn’t ship to basic training or draw a paycheck until months or years later — the date is set the day you signed.
The related date that causes constant confusion is the Pay Entry Base Date, or PEBD. Your PEBD marks the day you first began earning basic pay or drill pay, which is often later than your DIEMS. DIEMS controls your retirement system. PEBD drives other calculations, including continuation pay eligibility and, for people who considered the BRS opt-in, how many years of service they had accrued.1Defense Finance and Accounting Service. Blended Retirement System Frequently Asked Questions The two dates frequently don’t match, and each does a different legal job.
Where to Find Your DIEMS Date
Your Leave and Earnings Statement shows your DIEMS date in field 23, inside the entitlements and deductions section — not the identification block at the top.2Defense Finance and Accounting Service. How to Read an Active Duty Army Leave and Earning Statement Cross-check it against your Official Military Personnel File. The DIEMS data on your LES flows from your branch’s personnel command, not from DFAS, so pay side alone cannot correct an error.
Which Retirement System Your DIEMS Date Puts You In
Four systems exist. Your DIEMS date falls into exactly one window.
Final Pay: DIEMS Before September 8, 1980
If you signed in before September 8, 1980, you’re under Final Pay, the oldest system. Your pension is based entirely on your basic pay rate on the last day you serve. The formula multiplies 2.5 percent by each year of creditable service: twenty years produces 50 percent of that final basic pay, and thirty years produces 75 percent, which is the statutory cap.3Military Compensation. Retired Pay
Cost-of-living adjustments use the Consumer Price Index for Urban Wage Earners and Clerical Workers, averaging July through September and comparing to the same months a year earlier. If the comparison is negative, the adjustment is zero — the pension never decreases due to deflation. Very few active-duty members remain under Final Pay today.
High-36: DIEMS September 8, 1980 Through July 31, 1986
If your DIEMS falls in this window, you’re under High-36, sometimes called High-3. Instead of using your final paycheck, this system averages your highest 36 months of basic pay, which is almost always your last three years on active duty. The multiplier is the same 2.5 percent per year of service, hitting 50 percent at twenty years and 75 percent at thirty.3Military Compensation. Retired Pay Full COLAs apply once you begin collecting.
The practical difference from Final Pay is usually small — often a few hundred dollars a month — because most members don’t get a dramatic pay bump in their final month. The averaging just smooths out anomalies.
REDUX Election Window: DIEMS August 1, 1986 Through December 31, 2017
Members with a DIEMS date in this range default to the same High-36 calculation described above. What made this window different was the choice offered at the fifteen-year mark: stay with standard High-36, or elect REDUX and take a $30,000 Career Status Bonus upfront.4Defense Finance and Accounting Service. Career Status Bonus (CSB)/REDUX
Choosing REDUX carried real costs. The multiplier drops by one percentage point for each year of service below 30, so a twenty-year retiree gets 40 percent of the High-36 average instead of 50 percent. Annual COLAs are also reduced by one full percentage point compared to standard retirees.4Defense Finance and Accounting Service. Career Status Bonus (CSB)/REDUX Over a long retirement, that compounding COLA gap quietly erodes purchasing power more than most people expect when they take the bonus.
At age 62, the pension is recalculated as though the retiree had been under standard High-36 all along, restoring the higher multiplier.4Defense Finance and Accounting Service. Career Status Bonus (CSB)/REDUX That restoration is one-time. The reduced COLA rate continues after age 62, so the gap begins widening again.
Blended Retirement System: DIEMS On or After January 1, 2018
Everyone with a DIEMS date on or after January 1, 2018, is automatically enrolled in the Blended Retirement System. Members with a DIEMS between January 1, 2006, and December 31, 2017, had the chance to opt in during 2018, but that window closed on December 31, 2018.5Military Compensation and Financial Readiness. Blended Retirement System If you were eligible and didn’t opt in, you remain in your legacy system permanently.
BRS trades a smaller pension for a portable savings component. The pension multiplier drops to 2.0 percent per year of service, producing 40 percent of the High-36 average at twenty years and 60 percent at thirty.6Office of the Law Revision Counsel. 10 USC 1409 – Retired Pay Multiplier That’s roughly a 20 percent pension cut at the same years of service compared to High-36.
To offset the smaller pension, the government contributes to your Thrift Savings Plan account. An automatic contribution of one percent of basic pay begins 60 days after you enter service. After two years of service, the government matches your own contributions dollar for dollar up to an additional four percent, bringing the total possible government contribution to five percent of basic pay.7Defense Finance and Accounting Service. Defined Contribution (TSP) Fact Sheet You’re fully vested in all government contributions at the two-year mark. If you’re not contributing at least five percent, you’re leaving the full match on the table.
BRS members who have completed between 7 and 12 years of service (measured from PEBD, not DIEMS) also become eligible for continuation pay, a one-time cash payment in exchange for agreeing to serve at least three more years. For active-duty members the payment runs from 2.5 to 13 times monthly basic pay, with each branch setting its own rate inside that statutory range. Reserve members not on active Guard or Reserve duty see a smaller range of 0.5 to 6 times monthly basic pay.8Office of the Law Revision Counsel. 37 USC 356 – Continuation Pay: Full TSP Members With 7 to 12 Years of Service
Why the System Assigned to You Matters If You Leave Before 20 Years
This is the single most important practical difference between the legacy systems and BRS. Under Final Pay, High-36, and REDUX, a service member who separates before completing 20 years of service receives zero pension. None. The benefit is all-or-nothing at the 20-year threshold. Since roughly 80 percent of enlisted members and a significant majority of officers leave before 20 years, the legacy systems provided no retirement benefit to most people who served.
Under BRS, members who separate before 20 years keep their entire TSP account: their own contributions, all vested government contributions, and any investment growth. They lose the pension component, but they walk away with a real, portable retirement asset that can be rolled into a civilian 401(k) or IRA. That portability was the driving reason Congress redesigned the system.
Reserve and Guard: Same System, Different Collection Age
Your DIEMS date determines your retirement system regardless of whether you serve active duty or in a reserve component. A National Guard soldier who signed on January 15, 2018, is under BRS just like an active-duty Marine who enlisted the same day.5Military Compensation and Financial Readiness. Blended Retirement System
What changes for Guard and Reserve members is when they can start collecting. Reserve retirees generally cannot draw pension payments until age 60, while active-duty members can retire after 20 years regardless of age.9Office of the Law Revision Counsel. 10 USC 12731 – Age and Service Requirements Reservists also need 20 “good years” to qualify — years in which they earned at least 50 retirement points.10Military Compensation and Financial Readiness. Reserve Retirement
There is an exception for reservists called to active duty. For qualifying active service performed after January 28, 2008, the age-60 requirement drops by three months for every cumulative 90-day period served, with a floor of age 50. This reduction applies only to certain categories of involuntary activation and national emergency service, not routine training or voluntary active-duty orders.9Office of the Law Revision Counsel. 10 USC 12731 – Age and Service Requirements
Fixing a Wrong DIEMS Date
A DIEMS error can shift you into the wrong retirement system entirely, so catching it early is worth real effort. Start at your local personnel office. Many errors are simple data-entry mistakes that get resolved administratively with supporting documentation like your original enlistment contract or Delayed Entry Program agreement.2Defense Finance and Accounting Service. How to Read an Active Duty Army Leave and Earning Statement
If your branch’s personnel office can’t or won’t fix it, the formal route is filing DD Form 149 with your service’s Board for Correction of Military Records.11Executive Services Directorate. DD Form 149 – Application for Correction of Military Record Under the Provisions of Title 10 US Code Section 1552 Federal law requires correction requests to be submitted within three years of discovering the error, though the board can waive that deadline if you show a compelling reason for the delay.12U.S. Army. Applicants Guide to Applying to the Army Board for Correction of Military Records You must exhaust other administrative remedies before the board takes the case, and processing can run up to 12 months from when they receive your application.
Hold onto every enlistment document, ROTC contract, and DEP agreement you’ve ever signed. They are your best evidence if a DIEMS dispute surfaces years later, and reconstructing them from scratch is much harder than keeping the originals in a file.