This manuscript is concerned with stability analysis of sampled-data systems with non-uniform sampling patterns. The stability problem is tackled from a continuous-time point of view, via the so-called “input delay approach”, where the “aperiodic sampling operation” is modelled by a “average delay-difference” operator for which characterization based on integral quadratic constrains (IQC) is identified. The system is then viewed as feedback interconnection of a stable linear time-varying system and the “average delay-difference” operator. With the IQCs identified for the “average delay-difference” operator, the IQC theory is applied to derive convex stability conditions. Results of numerical tests are given to illustrate the effectiveness of the proposed approach.