1. 01 January 2010 is the reference date for calculating ages.
2. Determine how old a player will be on the THAT DAY of 01 January.
3. If he is 9 years or younger then he will be playing u/10.
4. If he is 10 or 11 years old then he is u/12.
5. And the same goes for the other age groups.
6. DO NOT SUBTRACT YEAR OF BIRTH FROM THE YEAR 2010 - THIS DOES NOT WORK AND GIVE WRONG ANSWERS.
An example: I was born on 01 January 1997. Today is 22 January 2009.
Today I am 12 years old. On 01 January 2010 I will be 13 years old. Thus, THIS year I MUST play at least u/14 in BOTH the team and individual events.
Another example. A player was botn on 20 December 1998. Today is 22 January 2009. Today he is 11 years old. On 01 January 2010 he will be 10 years old. Thus he MUST play at least u/12 in BOTH the team and individual events.
The above explanations is the EXACT way FIDE calculates ages and is so indicated in the FIDE handbook.
NB!!!! The FIDE website is WRONG - FIDE has admitted this - but is NOT yet updated. The website must NOT be used as a reference.
