Pinoko

Pinoko is a character from Black Jack. She was a Teratoma on a person's brain for 18 years, at which point she was transplanted into a robot body. That counts as her birthday, but she counts her teratoma years as part of her lifespan.

1 or 19
Apparently this occurred during spring since during winter as the following spring neared, she is legally 1 but 19 according to her standards.