When counting the number of the Israelites in Bamidbar 1 Moshe only counts those who are twenty and above which somehow seems to be the age of responsibility. After having refused to enter Canaan all those who were counted died in the wilderness.
Numbers 1:3 NIV
You and Aaron are to count according to their divisions all the men in Israel who are twenty years old or more and able to serve in the army
But all Jewish men become responsible for their actions at the age of thirteen. But when Moshe counted the Israelites he only counted those who were twenty years old and above.
Could the age of responsibility have changed from the time of Moshe to the present day?