Every October. They only do long-term-support (LTS) releases every two years, and those are always in April, so you're reading references to the most recent LT

Every October. They only do long-term-support (LTS) releases every two years, and those are always in April, so you're reading references to the most recent LTS release, 18.04. I'll be upgrading to 19.04 from 18.10, though.