Began 18 February 1958 · 355 days long
1958: year of the Earth
The year started on 18 February, not on 1 January — so anyone born in 1958 before that date is a .
If you were born in 1958
Born on or after 18 February — you are the Earth . Born between 1 January and 17 February — you are a , and every calculator that asked only for your birth year has been telling you otherwise. That is 48 days of 1958 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 1958
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 355 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 355 days, 1958 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.