The concept of time release provides a new mode of sending information to the future, where the message will be available after a certainly specified period. Time-release encryption (TRE), as a promising approach, has a widespread releasing application and ensures data confidentiality. TRE relies on two main frameworks, one based on the time-lock puzzle and the other based on a trusted third party, while this primitive is impeded by frameworks’ unreliability limitations and time disclosure. We present ReleaseSC, a decentralized and privacy-aware system that combines smart contract with TRE. ReleaseSC leverages a novel three-part architecture that harmonizes time release and contracts, enabling efficient time-hidden smart contract. Our prototype is with reasonable performance through EVM evaluations on both private chain and official test network. ReleaseSC is built on the top of a new cryptographic notion named ID-based TRE that supports a flexible time policy and preserves the to-be-released time. We propose an ID-based TRE instantiation and show rigorous security analysis in formal security models. The insight from ReleaseSC will open more possibilities to address security issues in hybridized cryptography-blockchain systems.