@vipucho it seems we are not yet on the same wavelength, so I'll try to rephrase that. All the events BEFORE this one (GTR34) had fixed start date and time, so everyone started at the same time and the event ended at the same time for all players.
This event was different. I don't know exactly when it became available, as I was off the internet, but someone said it was on Fathers Day. I do remember though, that when I entered the game, it showed something like "9d 14h remaining" and when clicking the event, I got a reminder it will last 5 days and whether I want to start it then or not (= wait). And since the date and time I started it, each 24 hours I got another chapter unlocked, and 24 hours to complete the last chapter.
And this is why I wrote "in your case", because some players may have the event already completed, while others were still eligible to start it and still finish it in time. I do not remember exact time limit, which is nowhere to be seen after starting (or even finishing) the event, which is why I cannot tell if it can still be started. Judging from the messages here, it cannot (while there are still players that do play it).