"Taxed and Spent" wrote

| Simple answer: just change it now.
|
| That is a simpleton answer.
|
| Is there anybody who can answer the question I raised?

It's a simple answer for a dumb question. If you
don't know when you last changed your password
then who would? If you think Yahoo does then ask
them. What other possibilities are there?

Or you could just change your password now.
You might also want to consider getting real email
(from your ISP, a paid account, or your own domain)
and not using Yahoo or other freebie webmail.