The Eclipse and Equinox projects follow a well established build and development rhythm. Getting to know this rhythm will help you to become a better Eclipse/Equinox contributor or committer. If you have a feature request or favorite bug that you'd like to see fixed, it's also useful to know about this rhythm so you can understand when is a good time to push on a bug, and to understand why your bug seems to be ignored for a long time and then suddenly get fixed much later.
Much like the earth, moon and sun have intertwined rhythms of rotation that create the days, tides, and seasons, the Eclipse project has a number of different layers to its development rhythm.
Each day at 8PM EST/EDT is the "nightly" build. These builds run against CVS HEAD, so whatever is in the repository at the time the build checkout occurs is what gets built and tested. Releasing code between 8-10PM is generally a bad idea because you may be caught in the middle of the checkout and cause compile errors in the build. Performance tests typically run on the Thursday and Saturday nightly builds, so if you have performance fixes you want to verify, getting them in before those builds is helpful. Any deviations from the regular nightly build schedule can be found on the releng build schedule.
On a weekly basis, integration builds are every Tuesday morning. Rebuilds occur if needed on Wednesday. These builds run against tags, so you can precisely what you want to release to the build, and when. If you release changes on Monday night there is no chance to verify in a nightly build before contributing to a real build, so extra care is needed when releasing last minute changes. A good time to release larger changes is around Wednesday after the weekly build is out of the way.
When there is a maintenance release under development, there are weekly maintenance stream builds on Wednesday at 8am EST with performance tests.