Apparently the party's location rotates between the towns. (Though they no longer mention "go here at 13:00".) I've only seen Westown and Tsuyukusa's birthday events (only in year two -reaching the next one-) but I tested it out to see if I could trigger Lulukoko's, and apparently it just rotates from Westown to Lulukoko. I think it was a nice touch. :D