Looking at the current Time skills in C# and Python, sometimes the code use the local culture, in other case the format is hard-coded and could cause unexpected results (e.g. when using the planner), e.g. month-day order being reversed only for some functions.

It would help adding a config to the skill constructor, so that a user can explicitly set which format/locale/culture setting to use in all functions.

See also comments on PR #927

/cc @tim-gill