A time-dependent angular analysis of decays is performed using data recorded by the LHCb experiment. The data set corresponds to an integrated luminosity of collected during Run 1 of the LHC. The CP -violating phase and decay-width difference of the system are measured to be and i5" class="mathmlsrc">i5.gif&_user=111111111&_pii=S0370269316305226&_rdoc=1&_issn=03702693&md5=45294b831db949d5bf74b33d8b7287a5">i5.gif">, respectively, where the first uncertainty is statistical and the second systematic. This is the first time that ϕs and ΔΓs have been measured in a decay containing the i56" class="mathmlsrc">i56.gif&_user=111111111&_pii=S0370269316305226&_rdoc=1&_issn=03702693&md5=4665416de8f1092f2090a62ab2b48a9e" title="Click to view the MathML source">ψ(2S) resonance.