The adoption of temporal expressions into SQL:2011 has continuously driven the extensions of temporal support in relational database systems (a.b.a. RDBMSs). In this paper, we present T-SQL, a lightweight yet efficient built-in temporal implementation in RDBMSs. T-SQL entirely relies on multi-version concurrency control (MVCC), widely adopted in RDMBSs, to manage temporal data. For temporal data, current records are maintained in legacy databases, and historical records, i.e., previous versions of current records (if any), which used to be periodically reclaimed are separately maintained in KV stores. To enable temporal query processing under SQL:2011, we extend the query engine in legacy RDBMSs to support query processing over either current records or historical records or both. Further, regarding temporal data are ever-increasing, we propose various optimizations to reduce the storage overhead of KV stores while keeping efficient query performance. We elaborate a publicly available implementation on how to integrate T-SQL into both centralized and distributed RDBMSs. We conduct extensive experiments on both YCSB and TPC-series benchmarks by comparing T-SQL with other temporal database systems. The results show that T-SQL is both lightweight and efficient.