There is no year zero, neither AD (CE) nor BC (BCE). Read bellow about these acronyms.
Below there is a set of steps to follow in order to convert number years to words...
1. For years of four digits (ie: 1000, 1435, 2000, 2018, ...9999)
2. For years of three digits (ie: 100, 137, 209, 357, ...999)
3. For years of one or two digits (ie: 1, 5, 10, 45, 137, 209, 357, ...999)
4. AD, BC, CE, BCE acronyms
1. For years of four digits (ie: 1000, 1435, 2000, 2018, ...9999)
1.1. For years ending with three zeros there is only one way of writing them out:
1000 = the year one thousand, in both American and British English words;
2000 = the year two thousand, in both American and British English words;
3000 = the year three thousand, in both American and British English words;
1.2. For years ending with two zeros there is only one way of writing them out:
1700 = the year seventeen hundred, in both American and British English words;
1900 = the year nineteen hundred, in both American and British English words;
2100 = the year twenty-one hundred, in both American and British English words;
1.3. If only the second and the third digit (hundreds and tens digits) are zeros, there are three ways of writing out the year:
1005 = the year ten oh five, in both American and British English words;
1005 = the year one thousand five, in American English;
1005 = the year one thousand and five, in British English;
2009 = the year twenty oh nine, in both American and British English words;
2009 = the year two thousand nine, in American English;
2009 = the year two thousand and nine, in British English;
1.4. If the second digit (hundreds digit) is zero, there are three ways of writing out the year:
1059 = the year ten fifty-nine, in both American and British English words;
1059 = the year one thousand fifty-nine, in American English;
1059 = the year one thousand and fifty-nine, in British English;
2010 = the year twenty ten, in both American and British English words;
2010 = the year two thousand ten, in American English;
2010 = the year two thousand and ten, in British English;
2018 = the year twenty eighteen, in both American and British English words;
2018 = the year two thousand eighteen, in American English;
2018 = the year two thousand and eighteen, in British English;
1.5. If the third digit (tens digit) is zero, then there are two ways of writing out the year:
1509 = the year fifteen oh nine, in American English;
1509 = the year fifteen hundred and nine, in British English;
1908 = the year nineteen oh eight, in American English;
1908 = the year nineteen hundred and eight, in British English;
1.6. In general, when the second and the third digits of the year are different of zero, write the first two and the second two digits as if they were single numbers. There is only one ways of writing them out:
1870 = the year eighteen seventy, in both American and British English words;
1878 = the year eighteen seventy-eight, in both American and British English words;
1970 = the year nineteen seventy, in both American and British English words;
1973 = the year nineteen seventy-three, in both American and British English words;
2110 = the year twenty-one ten, in both American and British English words;
2115 = the year twenty-one fifteen, in both American and British English words;
2. For years of three digits (ie: 100, 137, 209, 357, ...999)
2.1. For years ending with two zeros, there is only one ways of writing them out:
400 = the year four hundred, in both American and British English words;
600 = the year six hundred, in both American and British English words;
900 = the year nine hundred, in both American and British English words;
2.2. If only the second digit (tens digit) is zero, there are two ways of writing out the year:
105 = the year one oh five, in American English;
105 = the year one hundred and five, in British English;
702 = the year seven oh two, in American English;
702 = the year seven hundred and two, in British English;
2.3. In general, when the second digit of the year is different of zero, write the first digit separately, then the last two as a single number. There are two ways of writing them out:
497 = the year four ninety-seven, in both American and British English words;
497 = the year four hundred and ninety-seven, in British English words;
620 = the year six twenty, in both American and British English words;
620 = the year six hundred and twenty, in British English;
3. For years of one or two digits (ie: 1, 5, 10, 45, ...99)
3.1. Simply write the number out. There is only one way of writing out the year:
1 = the year one, in both American and British English words;
5 = the year five, in both American and British English words;
10 = the year ten, in both American and British English words;
13 = the year thirteen, in both American and British English words;
45 = the year forty-five, in both American and British English words;
99 = the year ninety-nine, in both American and British English words;
4. AD, BC, CE, BCE acronyms
You can place AD (or CE) before or after the year // OR // BC (BCE) after the year.
AD = Anno Domini (Latin phrase for "in the year of the Lord").
1 AD (or AD 1 in a stricter notation) is considered the year in which Jesus Christ was born.
Example: the current year, 2024, is: 2024 AD.
BC = Before Christ; years before 1 AD.
There is no year zero, neither AD nor BC.
Nowadays CE and BCE acronyms are also used.
CE = Common Era, instead of AD.
The year 1 CE = The year AD 1 (or 1 AD).
BCE = Before the Common Era, instead of BC.
Examples:
The year 1966 after the year 1 AD: AD 1966 = the year nineteen sixty-six AD (Anno Domini);
The year 1250 before the year 1 AD: 1250 BC = the year twelve fifty BC (Before Christ);
The year 1966 after the year 1 CE: 1966 CE = the year nineteen sixty-six CE (Common Era) = the year nineteen sixty-six AD;
The year 1250 before the year 1 CE: 1250 BCE = the year twelve fifty BCE (Before the Common Era) = the year twelve fifty BC;