To be announced (TBA), to be confirmed (TBC), and to be determined (TBD) are placeholder terms used very broadly to indicate that although something is scheduled or expected to happen, a particular aspect of that thing remains to be arranged. Although the phrases are often used interchangeably, they have subtle differences. "To be announced" implies that the aspect so designated may have already been determined, but is not yet suitable for public announcement. "To be confirmed" suggests that a decision has been made but awaits confirmation, although it is also used to indicate that the aspect to be scheduled remains open. Other similar phrases sometimes used to convey the same meaning, and using the same abbreviations, include to be ascertained, to be arranged, to be advised, to be adjudicated, to be done, to be decided, and to be declared.
Use of the abbreviation "TBA" is formally reported in a reference work at least as early as 1955, and "TBD" is similarly reported as early as 1967.