Astilbe is just starting to bloom here. Maybe your neighbor's plants are in a bit more sun? That could cause an earlier bloom cycle. Astilbe like a moist, organically enriched soil with just a bit of direct sun and even first year plants will bloom reliably if provided with these conditions.

In addition to what GG48 said, there are different hybrids, and they might bloom at slightly different times, depending on their genetic make-up. I have some, A. chinensis, that blooms much later than all my others, usually in early August.

What NHBab's said. I have some blooming now and will have other varieties blooming from now through August. I am in zone 3/4