Data staleness is one of the most important factors leading to low data quality. It highlights the needs of determining the currency of data to identify whether a database is up-to-date. There are some works on determining data currency, but all these methods have their limitations. Some works require timestamps which are always invalid, and others are based on certain currency rules which can only decide relevant currency and cannot express uncertain semantics. To overcome the limitations of existing methods, this paper introduces a new approach for determining data currency based on uncertain rules. A new class of uncertain currency rule is first introduced. Based on the uncertain rules, mathematical models of data currency are proposed. Two algorithms to determine data currency are developed. A method of automatically learning the uncertain currency rules is also provided. Using real-life data, the effectiveness and efficiency of our methods are experimentally verified.