# Survival analysis - different start times

I am doing a survival analysis on vending machines based on their time to failure.

However, my machines are deployed in 4 main locations, machines are all installed at a different time depending on location.

Do I need to include the machine's start date as a feature in my model? Or do library models like those provided by pysurvival only need to know the time to failure regardless of installation date?

If you feel that the machine's reliability is correlated to start date (for example, due to improved installation experience), then yes, you should include it as a feature (probably as a start date - <some arbitrary date>-like variable).