Here is the full list of all 22 Timelie achievements. It takes around 8-10 hours to unlock all of the achievements on Windows.
Complete "This Is Cat. Can You Hear Me?" relic challenge.
Collect the 1st Memento.
Complete "If It Is Broken, Don't Fix" relic challenge.
Complete "Well Planned!" relic challenge.
Complete "A Quiet Place" relic challenge.
Complete "3-2-1-GO-1-6-7-8" relic challenge.
Complete "It'd Be Too Damned Easy" relic challenge.
Complete "Time Waits For No One" relic challenge.
Complete "Retcon" relic challenge.
Complete "The Most of Us" relic challenge.
Complete "I Come in Peace" relic challenge.
Complete "Urnique" relic challenge.
Complete "Omen" relic challenge.
Collect the 2nd Memento.
Collect the 3rd Memento.
Collect the 4th Memento.
Complete the story of Timelie.
Watch the secret ending.
Obtained all Timelie achievements.
Complete "Splinter Cat" relic challenge.
Complete "I'd Like To Have That In Writing" relic challenge.
Complete "Operation Skuld" relic challenge.