You can choose whatever you want for whatever reason... but if you make up your own rules and definitions, please don't try to push them in already existing and accepted definitions and distinctions.

The Gregorian calender start at year one and not at year zero, deal with it. Since every century is by definition exactly 100 years (not 99 years or any other number of years), every following century based on the Gregorian calender also has to start at xx01 and not at xx00.

Nope, in your example if he's born the 1st of July 1900 he is born in 1900,5 and NOT 1899,5

1900 is the beginning of the new century which means that if he's born in the middle of the year 1900 he starts living when the century is half a year old. (1900 + half a year which is 0,5 = 1900,5)

Just as when you are born you are ZERO years old and NOT minus 0.5 years old nor 1 year old.

Just to be clear, all this using the decimal system (mathematics) and not the Gregorian count.

EDIT: And there is no 0th year, there is the FIRST year but as long as the FIRST year is not complete you are in the year zero (when counting in whole numbers) if you count in fractions then it's different but no one counts years in fractions when speaking of the year of an event so that's why we consider whole numbers and not fractions here.

Ok last time I answer this kind of message. I don't make any rules I follow logic and mathematics. I explained time and again why and how. If you or others still don't get it, that's it for me. I will not debate logic and mathematics, you can debate religion, politics, video games etc. but you cannot debate mathematics. 1+1=2 and if you start debating that it is equal to 3 you make no sense and I can't help you anymore. But saying it equals 3 is not an option or an opinion.

Come to think of it the only point you and others can debate is to say you choose to follow the Gregorian calendar over mathematics. That's an opinion, I would disagree but it's still an opinion. But debating mathematics is not an opinion, it's a waste of time.

Omg :0

I tried to be as clear as possible but it didn't came trough your mind. I don't know what to say, what you state is simply wrong. 

When a car crashes in the middle of the lap 3, it made 2.5 laps starting from the beginning point, which is in this case, the starting/finishing Line. And absolutely not 3.5...

You're making the mistake i mentionned with the beginning point. 

Year 1 is not the year that begins when one year has passed since the beginning point, it is the first year starting immediatly after the beginning point.

In that case you should be consistent and call this century the 20th century as all the numbers start with 20.
Except the zeroth century doesn't sound all that great, though mathematically correct :p

What's year 1 of your life? From birth until you turn 1? Or from 1 until you turn 2?

We're in the 18th year of the 21st century, because the century started at 2001. Mathematically we currently are in the 19th year. The 100th year of the 20th century was the year 2000.

What's the zeroth letter of the alphabet :)

Mathematics can only define the length of a century (one hundred years), NOT the arbitrary beginning point of a calender. They day when the year (and a decade, century and millenium) begins is also arbitrary... so is the day of the birth of Jesus (many historians doubt that it was even in December).

Exactly a car crash in the middle of lap 3 is indeed 2.5 laps from the beginning point. I never said in THIS CASE that it would be 3.5

I say that if you are born in July 1900 you are born INSIDE the 1901st year but the 1901st year is NOT complete since you are ONLY in the middle of it ok? but once 1900 is FULLY FINISHED you arrive in 1901 (as in 1901 complete years having passed) and you begin the 1902nd year which you call 1901 cause the 1902nd year is NOT COMPLETE, you see?

Your mistake is to assume that July 1900 is the middle of the 1900th year when in fact it's the 1901st year. When you say January 1, 1900 it means that mathematically speaking 1900 years have PASSED, so you are BEGINNING the 1901st year which you call 1900, do you see what I mean?

That sure is a lot of words to commit to something that is verifiably wrong lol... seriously, just go google "when did the 20th century start?" Feel free to disagree with the norm, but don't tell other people they're wrong heh

Look at it this way: Year one includes all days of said year, from 1/365 of a year to the final 365/365 day of that year. Thus, a century is not over until the entirety of the 100th year has actually played out. Once you've reached 1901, for instance, you are finally beginning to fill out the first year of a new century. 

To show it purely in numbers, the first year of a new century is represented by the number "1", but in reality when broken into days is actually 1/365. Thus, to change the century at 1900 would leave you with only 99 years... it is not until that 100th year has actually been completed that a full century has passed. So basically 1900 is actually 99 1/365 - 99 365/365, also known as 100.

*edit* Yikes just saw that you're still in denial... it's alright man, we all make mistakes from time to time, you don't need to bunker down and defend said mistakes. :p

What?

Not at all, you cannot call this century 20th. Since 2000 years have ALREADY passed that means 20 centuries have ALREADY passed. Now we are in years that come AFTER 2000 years past so since 20 centuries have passed, this one is the 21st. We are 20 centuries old in our history YES, but we are in our 21st century, this 21st century is NOT COMPLETE since we are still inside it ok? So we cannot say our history since the beginning of this count is 21 centuries old, we can say it's 20 centuries old and we are currently in the 21st.

Year 1 of your life is from birth until you TURN 1, that's your FIRST year, but you are NOT 1 year old UNTIL you actually live one full year. ONCE you have lived 1 year and mom and dad sing you the happy birthday to you song, you are 1 year old living in your SECOND year of life but you don't say you are 2 years old just because you are living in your second year of life, you STILL say you are 1 year old UNTIL you FULLY complete your second year of life, then you will say you are 2 years old and you will be living your 3rd year of life etc...

How is that not clear?

There is no calling the first letter of the alphabet zero because a letter cannot be divided. You don't have half a letter or part of a letter. You have a full letter. And if you want to quantify a letter then you can say the alphabet starts at zero when there is no letter and is at 1 when you have set the first letter.

Who was your math teacher at school (you and the others who still don't get it) cause he/she deserves to go to prison or something

Honestly if you decided to replace your brain by using Google, well that may be fine. Let's just hope Google never goes away for your sake...

Also if you don't follow the entire debate from the beginning, you are not going to get what is being said.

The first year of a century is represented by the number 1 in the GREGORIAN calendar (you'd know this if you had followed this issue from the beginning) but since you choose to butt in without even knowing all that has been said, well... yeah, Google!

Anyway first year as number 1, yes. Why? cause the Gregorian calendar made the mathematical mistake of calling it 1 instead of calling it 0.

Now in case you don't know, any mathematical counting in our decimal system begins at ZERO and not 1. Just as the first year of your life is called FIRST but if you must say what your age is in terms of YEARS, you are ZERO years old. you can ONLY be 1 year old once you have LIVED a full year. Google this if you don't believe me.

Second year of your life you are now 1 year old, third year of your life you are 2 years old and so on... Get it so far?  In other words the first century of a count that is mathematically CORRECT would start at January 1 of year 0 then after a full year of doing whatever you want, you get to January 1 of year 1 cause a full year has passed and therefore you can say it's the year 1, it will be the SECOND year but only 1 FULL year has passed. AFTER a SECOND year has fully passed you can start saying it's the year 2 and you'll be in the third year etc...

Now it's alright that you made a mistake. It seems that logic is not something everybody masters, just think logically and you will see what I mean... or keep denying it, in which case, yeah Google.