Manager: yo I need a time line for this shit.
Me: I don't know how long it takes.
Manager: tell me how long it takes.
Me: I can tell you what can be done in next couple hours. I don't even know what will happen tomorrow.
Manger: now tell me this time shit.
Me: .......

Seriously, dear fellow ranter. How do you estimate timeline? Your timeline is changing.

I tell management twice what I think it will take if I had all the time in the world and no meetings. If anything tell them 336 hours.

People like timelines..

Beak down the task into small parts and estimate each part. Work it out as if you were working on that one thing and round up. If there is a part with a lot of unknowns then just give it a high ball-park eg. two weeks. If there is a lot of unknowns add the first part of the timeline as investigation of the unknown.

Next guess your productivity factor. For example if you are doing support+development you may only have 50% time for development.

Draw up each activity into the timeline representing real world time. Present the timeline but give warning not to hold you to it until the unknowns are filled out. Later revisit the timeline and adjust it based on your progress or changes in requirements.

If the overlord asks you to do it quicker it is a trap. Never ever say that if you work really hard maybe you could. You work hard anyway right? Of course you could offer alternatives for example maybe they change your workflow so you don't answer support calls, etc.

Start estimating everything you do:put a number on every task before doing it, it doesn't have to be hours, then after a while you can average how much the numbers you give to task means in hour.

That will improve estimation, and give you a better handle on what's hard to estimate.

After a while, your estimations will start being a lot more precise.

Better yet, involve the manager in those estimations, and reflect on how it went from time to time.

After a while, start slowly shifting the blame of being late on your manager, there are multiple ways he can dig his own grave: adding unplanned work, transforming estimations into deadline, failing to allocate time for bugfix/maintenance.

You can do that because everything, by that time, will be accounted for.

Remember: while it's your job to estimate, it's HIS job to plan and work around delays.

You can estimate time it will take you to break down task into smaller pieces and estimate how long they will take separately. Usually a day in my experience for small tasks.

I usually just take a number from my ass, multiply it by pi and tell them that number in days. I’ve been meaning to write a book about this method it but my estimated time to finish the book it is too high.