Effective Date

The date, declared by the Securities & Exchange Commission (SEC), on which shares can start trading. This usually refers to the date when shares become available for sale in an initial public offering.

Investopedia Says:
The effective date occurs approximately 20 days after the security is registered with the SEC, giving time for the SEC to review the registration. The registration will be either accepted or rejected by the twentieth day or earlier. Amendments can be made to the registration if the SEC deems that changes are necessary. If the items in question are not modified, the registration process is not completed.

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Date on which a transaction is posted, or an agreement becomes effective.

1. Banking. The time when an expiring Certificate of Deposit is renewed at the current rate, and interest paid is adjusted accordingly. Also, the date on which a bank card becomes valid.

2. Securities. The date on which a registered offering of securities may be sold, ordinarily 20 days after filing of the issuer's registration statement with the Securities and Exchange Commission. See also Shelf Registration.