➥ How to check when ubuntu was installed

command:
sudo dumpe2fs /dev/sda1 | grep 'Filesystem created:'


result
root@ro22proxy3:~# sudo dumpe2fs /dev/sda1 | grep 'Filesystem created:'
dumpe2fs 1.42.13 (17-May-2015)
Filesystem created: Tue May 9 13:24:21 2017