5 CFR § 892.203
When will my premium conversion begin?
November 4, 2020
If you are newly employed or newly eligible for FEHB in a covered Executive Branch agency (as described in §892.201(a)), your salary reduction (through a Federal allotment) and pre-tax benefit will be effective on the 1st day of the first pay period beginning on or after your employing agency receives your enrollment.
[68 FR 56528, Oct. 1, 2003]