Plant phenology is an important indicator of the impact of global change on biological systems because it is very sensitive to climate change. Flowering phenology is of great importance since it represents the major developmental transition of plants from the vegetative to the reproductive stage. Many existing studies have identified the advancement in first flowering date in response to global warming. However, the mechanism of first flowering date dependency on climate change remains obscure. Plant hormones play pivotal roles in almost every aspect in plant life including flowering. To understand the regulation of plant flowering phenology in response to climate change by plant hormones, accurate and efficient measurements of plant hormones are required. In this review, the functions and possible links between plant hormones and the change in first flowering date were discussed. Also, recently developed methods for plant hormone detection were briefly summarized, providing scientific techniques for understanding the underlying mechanisms of plant phenology in response to environmental stimuli.