Entweder so
x1=$(date +%Y -d "last year")
x2=$(date +%Y)
x3=$(date +%Y -d "next year")
for v in "x1" "x2" "x3"; do
echo ${!v}
done
oder als array
x[1]=$(date +%Y -d "last year")
x[2]=$(date +%Y)
x[3]=$(date +%Y -d "next year")
for ((n=1; n<4; n++)); do
echo ${x[$n]}
done