How to Calculate Service Computation Dates

The Service Computation Date, also known as the SCD, determines when a federal employee becomes eligible for a specific benefit. These benefits include pay raises, vacations, promotions and retirement pensions. The SCD accounts for when the employee was initially hired, when he separated from his employment and any time he spent on leave between those dates. The final calculation allows benefits administrators to judge when and if the employee is eligible to receive benefits.

The federal Office of Personnel Management defines the "effective date of appointment" as a date, either actual or constructed, used to determine benefits based on how long the person has been working in a federal agency. Benefits administrators use the federal employee's effective date of appointment as the start date for her benefits eligibility. The effective date may be the employee's first day on the job, or it may be a date derived from the employee's agency, position or years of service.

Federal employees with prior military or civilian experience can use their time toward calculating their SCD. The employee's prior experience, known as "creditable service" time, goes toward "rolling back" his SCD. For instance, a Marine Corps veteran takes a civilian position at the Pentagon. The veteran was discharged after three years, 11 months and 25 days of service. The start date for the civilian position is Dec. 31, 2014. The SCD would be Jan. 6, 2011 after making an adjustment for his service.

If the employee has been separated from federal service for more than three consecutive non-paid days, these service separations also go toward calculating the SCD. Since these employees have not contributed to the federal employee benefits programs during their separation, they must make up that time to be eligible for those benefits. Using the example above, the Pentagon worker has been separated from both military and civil service employment for six months. The new SCD would be pushed forward six months to July 6, 2011.

Some civil service departments may experience cutbacks on the number of employees they maintain on staff. These cutbacks, known as a "reduction in force," are similar to layoffs in the private sector. Administrators use the SCD to determine which employees they will retain and which ones they will release. They can also adjust the SCD based on the employee's previous performance ratings. Employees with an earlier adjusted SCD are more likely to be retained.