Aspects of the present disclosure relate to techniques for determining timing of uplink transmissions for UEs communicating with carrier aggregation involving both frequency division duplexing (FDD) and time division duplexing (TDD) component carriers (CCs). A timing advance (TA) offset value for a user equipment (UE) to use for uplink transmissions is determined based, at least in part, on which of the CCs carries a physical uplink control channel (PUCCH).