I was reading through the tweets on the post here: https://kotakuinaction2.win/p/13zfvbCRTn/australia-if-you-havent-had-a-va/c/

A Twitter user posted a collage about a number of places all mandating vaccination by October 15th. What's interesting is that the date isn't local for just any single region. As you already know there's Victoria. Australia: https://archive.is/l4Brb

Massachusetts also has an October 15th deadline: https://archive.is/VoB08

Unless unvaccinated workers decide to take the one-dose Johnson & Johnson vaccine by Friday, they will not meet the city’s Oct. 15 deadline.

Wales has a mid-October deadline, too: https://archive.is/HeyJp

All 12 to 15-year-olds in Wales will be offered a Covid vaccine by the end of the October half-term, the Welsh health minister has said.

Ottawa has an October 15th deadline: https://archive.is/XU8Uv#selection-2169.0-2169.171

The University of Ottawa's president said last week about 91 per cent of its students and staff were fully vaccinated. Its deadline to be fully vaccinated is also Oct. 15.

Quebec has an October 15th deadline: https://archive.is/K6PxO

Unvaccinated health-care workers will be suspended Oct. 15

California has an October 15th deadline: https://archive.is/XjGLN

Friday’s announcement comes about two weeks ahead of an Oct. 15 deadline for California teachers to be vaccinated or submit to regular testing.

Delhi has an October 15th deadline: https://www.livemint.com/news/india/delhi-school-teachers-and-staff-must-get-vaccinated-by-october-15-or-else-11632972518175.html

Another article just to drive the point home: https://www.ndtv.com/delhi-news/delhi-schools-october-15-vaccine-deadline-for-delhi-government-teachers-school-staff-2559146

Delhi school teachers and staff must get vaccinated by October 15 or else...

Even Angola has an October 15th deadline: https://www.independent.co.ug/angola-declares-covid-19-vaccination-mandatory-for-adults/

Angola on Thursday made it mandatory for citizens 18 years or older to take the COVID-19 vaccine by Oct. 15.

Italy also has an October 15th deadline: https://archive.is/ETkCI#selection-513.0-513.177

Officials said Prime Minister Mario Draghi's unity government would approve the move at a cabinet meeting later in the day, with the new rules due to come into force on Oct. 15.

I'm sure there are more, but it would require more time than I care to spend on this since I have other things to do. However, it does reminds me of the "Gamers are dead" synchronization.