You have posted before that the rubrics after the Ember Saturday Mass in the octave of Pentecost read “Post Missam exspirat tempus Paschale.” However, in the breviary, it reads “Post nonam, terminatur Officium proprium de octava, et explicit tempus paschale…” So when does Easter time really end?
Since you mention the Octave of Pentecost – appallingly obliterated for the Novus Ordo – I’ll stick to the traditional Roman calendar
Insofar as Holy Mass is concerned, the last Paschaltide Mass would be that Saturday morning. We assume that Mass is said in the morning.
However, the liturgy is more than the Mass.
By the way, it really gripes me when people refer to Holy Mass simply as “liturgy”. But I digress. “Hello, Eyebrow of Jesus Catholic Community, how may I direct your call? … What time is Sunday… Mass? Well, we have liturgy at 9 and 11 if that’s what you mean.”
As far as the whole of the Roman liturgy is concerned, which includes the Office, Paschaltide ends after the recitation of Nones on Saturday. Thus, the Time after Pentecost begins with 1st Vespers of Trinity Sunday, which properly recited Saturday in the afternoon sometime. You just don’t see the green yet, for 1st vespers or for Mass, because Trinity Sunday white trumps the green. But I assure you, the green is really there. It’s just spiritual, invisible green.