The "Default Date" would be Tuesday, August 2nd.
Social Security checks/direct deposits (for regular SS and disability) are made on a Wednesday based on ones date of birth:
Second Wednesday: Date of birth 1st -- 10th; Third Wednesday: Date of birth 11th -- 20th; Fourth Wednesday: Date of birth.
Supplemental Security Income (SSI) checks/direct deposits are made on the 1st of the month. Those receiving both SSI and regular SS and/or disability are on a different schedule.
OPM FERS/CSRS Annuity checks/direct deposits are made the 1st of the month (or the last day of the prior month).
Therefore, most likely, there will be no issues in those receiving OPM FERS/CSRS Annuities for August. If there is a default and the matter goes into the second week problems with payments will begin to develop with Social Security payments. Furthermore, if it should continue to August 31st/Sept. 1st. there could very likely be problems with Sept. OPM FERS/CSRS Annuity payments.