The dates I've recieved the anniversary stamp

Its that time where i come back and say sometging weird again… why are the dates diffrent lol its an anniversary

You’d need to ask the Discourse developers (or read the source code) to find out. I’d take a guess that as the time of day when the badge is granted is also different is that the background job to grant the badges either is triggered with a timer that isn’t exactly one year long or due to differing load on the server the job to check the badges takes different amount of time to process.