TSVer: A Benchmark for Fact Verification Against Time-Series Evidence

Reasoning over temporal and numerical data, such as time series, is a crucial aspect of factchecking. While many systems have recently been developed to handle this form of evidence, their evaluation remains limited by existing datasets, which often lack structured evidence, provide insufficient justifications for verdicts, or rely on synthetic claims. In this paper, we introduce TSVER, a new benchmark dataset for fact verification focusing on temporal and numerical reasoning with time-series evidence. TSVER contains 304 real-world claims sourced from 41 fact-checking organizations and a curated database of 400 time series covering diverse domains. Each claim is annotated with time frames across all pertinent time series, along with a verdict and justifications reflecting how the evidence is used to reach the verdict. Using an LLM-assisted multi-step annotation process, we improve the quality of our annotations and achieve an inter-annotator agreement of κ = 0.77 on verdicts. We also develop a baseline for verifying claims against timeseries evidence and show that even the state-ofthe-art reasoning models like Gemini-2.5-Pro are challenged by time series, achieving a 63.57 accuracy score on verdicts and an Ev 2 R score of 47.36 on verdict justifications.