In determining an individual's entitlement to an annuity and the amount of annuity to be paid under the Railroad Retirement Act, a calendar month or part of a calendar month during which the individual was in the active military service of the United States in a war service period, or period of national emergency, as determined in § 212.4 of this part, may be included in the individual's years of service. Military service is credited as though the individual had performed service for a railroad employer as provided for in part 210 of this chapter, provided that the individual is credited with railroad service in the year of or the year before entrance into active military service. Compensation for creditable military service shall be credited as provided for in § 211.7 of this chapter.