Began 15 February 1991 · 354 days long
1991: year of the Metal
The year started on 15 February, not on 1 January — so anyone born in 1991 before that date is a .
If you were born in 1991
Born on or after 15 February — you are the Metal . Born between 1 January and 14 February — you are a , and every calculator that asked only for your birth year has been telling you otherwise. That is 45 days of 1991 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 1991
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 354 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 354 days, 1991 was an ordinary year of 12 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.