[pas]

Initial estimation (over many sprints, with either a greenfield project or with a new dev team) is always very hard, almost a completely foolish attempt.

After the first few sprints the uncertainty reduces.

And after the team gains experience with the system (business domain + codebase + infrastructure - if applicable), they are much better at scoring tickets (SCRUM poker), which then can be converted back to time from points.

Directly estimating time (asking for time estimate from programmers) is just something that never works (or if it does, then it means the programmers does the following adjustment internally), as humans get into the confusion of constantly having to recalculate their intuitive feeling of required time based on how long actually that took the last time they felt that.