If you mean "in a season" (The Sims 3 Expansion Pack), the unicorn spawns quite frequently throughout the year.
ຖ້າທ່ານ ຫມາຍ ຄວາມວ່າ "ໃນລະດູ ຫນຶ່ງ" (The Sims 3 Expansion Pack), ນ້ ໍາ unicorn ມັກເກີດຂື້ນເລື້ອຍໆຕະຫຼອດປີ.