Mines showing the correct date............. have you clicked on a "Like" someone gave for an old one ???? ... I came across something similar recently and was a bit confused (more than Normal) for a little bit......
I have found that if I click on an alert notice it seems to go to the start of the thread not the actual post, that can be 10 years or more ago...........Server could be in Victoria so in lockdown....
You're lucky Alan, I'm stuck in 2020 Melbourne .... I'd do anything to be in 2015 (Id certainly ensure Dan Andrews didn't get elected, while your in 2015 maybe you could have a look at that)