2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6144Both GONG and MDI projects have measured {\it p}-mode frequencies of the Sun for more than 7 years. Here we review what we have learnt from the temporal variation of the oscillation frequencies and splitting coefficients.6 pages, Latex (requires Basi.sty), invited review presented in the annual meeting of ASI (2003)Astrophysicstext