It all depends on what kind of project. In general projects will depend on the kind of industry we are targeting, what value will add to the product or project to make it better for customer experience or the process.
Let’s take an example here ( iOS)
It’s one of the most popular mobile operating systems in the world. This OS has evolved over the years. It will be built with many internal projects.
In Apple, Internal KeyNote, AppStore, Apple Music or Apple Pay or Calculator there are a bunch of apps , it will be built by independent teams tracking different projects.
Apple Pay is a new service built by Apple. This project might take a year or more to launch to the public with all validations and trials.
This project will be a multi year project.
Calculator: This product might be built in a year and later it may be moved to maintenance mode due to less number of new requirements.
WebSite: it might be built in a day, week, month , year or multi year.
In general Project development - will follow the lifecycle
Initiating - Project Ideation, Market research
Planning - Based on market research, list out most important features and time for execution ( includes budgets, resource allocation, technology and marketing strategies)
Monitoring - Keep Eye project progress and change plans based on current situations to inline with planning.
Controlling - Ensure everything falls under budget and timelines.
Closing - divide project into multiple tasks,if something not inline plan, close it
As per current conditions We need to Fail fast if something does not work.
Coding will be part of project planning, it will be done in a week with less number of offerings vs more developers.
I will add that there are a few additional factors to consider to understand how long it takes to code for a project. 1) The members of the project team...what is their coding skill set? How long have they been coding in a specific language? Can they code in the language they know or will they have to learn a new programming language? 2)How many clients are there meaning how many people could/should have input in the project? As a hint, in general terms, small groups tend to move faster :) 3) Will the output of the project become the input of another project? This may matter in design to ensure that expectations on results are consistent.
For sure there can be a vast difference in how long it takes if you are building something new vs updating something that is already up and running.
Hope you find this answer helpful and best of luck to you!