DateTime creation on boundaries of Daylight Savings Time
Creation of local DateTimes at the start and end of DST are
Between the start date and time of DST and one hour later, there
is no local time. Attempts to create a local DateTime in this
non-existent range do not fail, they return the DateTime one hour
Between the end date and time of DST and one hour earlier, the
local Time is ambiguous; there are two distinct DateTimes that
are correct representations of the local time. The current
creation mechanism returns the DateTime of the later of the two.
Consequentially, there are certain GMT DateTimes (the earlier
of the two for an ambiguous local time) that it is not possible
to create using the DateTime local time creation methods
Use the DateTime gmt creation methods to avoid the inherent
ambiguity of the local time at the DST boundaries.