View Mercury retrograde periods with exact UTC station times, zodiac degrees, signs, and pre- and post-shadow dates. Free, no sign-up required.
Mercury is retrograde when its apparent geocentric tropical longitude decreases. This calendar finds the exact station when Mercury's longitudinal speed crosses zero instead of relying on hand-maintained date lists. The pre-shadow begins when direct Mercury first crosses the later direct-station degree, and the post-shadow ends when Mercury clears the earlier retrograde-station degree.