Began 22 January 2004 · 384 days long
2004: year of the Wood
The year started on 22 January, not on 1 January — so anyone born in 2004 before that date is a .
If you were born in 2004
Born on or after 22 January — you are the Wood . Born between 1 January and 21 January — you are a , and every calculator that asked only for your birth year has been telling you otherwise. That is 21 days of 2004 assigned to the wrong animal by the usual method.
The across the cycle
The animal returns every 12 years but the element every 60, so each of these years is a different .
Lunar years around 2004
Lengths differ because a leap month is inserted every two or three years. This is what makes the new year date jump rather than drift.
Why 384 days, and not 365
The Chinese calendar counts lunar months of about 29.53 days. Twelve of them come to roughly 354 days, eleven short of a solar year, so a thirteenth month is inserted every two or three years to keep the calendar aligned with the seasons. At 384 days, 2004 was one of those leap years, carrying 13 lunar months.
This is also why the new year date jumps around instead of drifting steadily: it moves back about eleven days each ordinary year, then forward by roughly nineteen when the leap month arrives.