Prime Earth WW was born in the late 20th century - she's the last child of Zeus. IIRC, she was 23 years old at the start. However, as part of Grail and Myrina's origin, her birth was depicted as during Greek antiquity.
The time frame is unclear; dates or ages are rarely mentioned. For Earth-Two she was created at least after the labour of Herakles. For Earth-One, she was sculpted at least 1000 years into the existence of Paradise Island, also after Herakles. Herakles, while fictional, is usually placed around 2000 BCE. So she could be 3000-ish years old pre-Crisis