How to estimate programming time

How much time will it take?

Junior Engineer: Does some simple math to estimate the best possible scenario. Gives that number.

Senior Engineer: Spends extra time to parse out the time cost of each individual piece, carefully adding buffer on each one, then eventually multiplies that number by something arbitrary (X2 to X10 depending on type of dev). Holds this number in his/her head then goes to the person that requested the work and evaluates the person. After evaluating this person the Senior Engineer says a number that is at the absolute furthest reach of what the requester ever thought it could take. Waits for a reaction. If the requester says okay, or decides they don't think its worth it, the senior did their job properly. If the requester asks if it can be done in an amount of time that is significantly less than the number the Senior gave. The Senior should smile, nod, leave, and immediately start working on finding their next job.