IndyMac reported that during April 2008, Moody's and Standard & Poor's downgraded the ratings on a significant number of Mortgage-backed security (MBS) bonds including $160 million of those issued by IndyMac and which the bank retained in its MBS portfolio. IndyMac concluded that these downgrades would have negatively impacted the Company's risk-based capital ratio as of June 30, 2008. Had these lowered ratings been in effect at March 31, 2008, IndyMac concluded that the bank's capital ratio would have been 9.27% total risk-based. IndyMac warned that if its regulators found its capital position to have fallen below "well capitalized" (minimum 10% risk-based capital ratio) to "adequately capitalized" (8–10% risk-based capital ratio) the bank might no longer be able to use brokered deposits as a source of funds.

When did Moody's and Standard & Poor downgrade a significant number of IndyMac's MBS bonds?