44 CFR §150.10

Nominations may only be submitted for acts, services, or contributions occurring within two years preceding the November 15 cut-off date described in § 150.3(c) of this part. However, nominations submitted prior to the February 28, 1985 cut-off date may be made for acts, services or contributions occurring on or after October 29, 1972 (two years before the effective date of the Act).