The Lamb: Offered in Sacrifice: At a Year Old
Source: TTT
Exodus 12:5
Your lamb must be an unblemished year-old male, and you may take it from the sheep or the goats.
Numbers 6:14
and he is to present an offering to the LORD of an unblemished year-old male lamb as a burnt offering, an unblemished year-old female lamb as a sin offering, and an unblemished ram as a peace offering—