ANG-7045: Fix moon.Calendar calculation of month days.

Issue
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With upcoming `ilib` changes that fix known issues with Gregorian month days, `moon.Calendar` is now updated to take advantage of this fix.

Fix
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Remove the "-1" adjustment of the month day in favor of passing in the unixtime with local timezone. Also, implement more efficient way of initializing calendar instance.

Enyo-DCO-1.1-Signed-off-by: Aaron Tam <aaron.tam@lge.com>