[boost] [chrono] Dependency on math?

The latest dependency report shows chrono as having a dependency on math. See http://www.pdimov.com/tmp/report-develop-3b5a9f4/module-overview.html math is really big. In testing bpm, an install of timer (which depends on chrono) slowed noticeably when it got to math. Presumably the build is also much slower, although I haven't tested that yet. Is the math dependency really needed? Thanks, --Beman