Joan London the Australian author (born 1948) is a separate figure from Joan Lunden the American television host (born September 19, 1950). Given the name alone, it could refer to either, so the intended person matters for accuracy. If you mean Joan Lunden:

• She was born on September 19, 1950, in Fair Oaks (Sacramento area), California, USA. As of today, her age would be 75 years old. If you need precise age in years and days, that would depend on the current date relative to September 19.

If you mean Joan London (Australian author):

• She was born in 1948 in Perth, Western Australia. As of today, she would be in her mid-70s, depending on whether her birthday has occurred this year.

If you can specify which Joan London/Lunden you’re asking about (Australian author Joan London vs. American TV host Joan Lunden), I can confirm the exact birthdate and compute the current age precisely.