Kepler-186b is the innermost planet and the smallest of its system, and thus not suitable for life. The orbital period of this planet is just under four Earth days long due to its location near the parent star.[3]
It is tidally locked. As a result, one hemisphere is in eternal daylight while the other hemisphere is in endless darkness.
The other planets in the system are Kepler-186c, d, e, and f, of which only Kepler-186f is within the habitable zone.
References
^ abc"Kepler-186 b". NASA Exoplanet Archive. Retrieved 29 December 2016.