MONGOID-5425 Verify string mongoization into Date, Time, DateTime with time zones (#5387)

* MONGOID-5425 Verify string mongoization into Date, Time, DateTime with time zones

* MONGOID-5425 fix CI tests

* add docs

Co-authored-by: Oleg Pudeyev <[email protected]>

Author: neilshweky

source/reference/fields.txt

@@ -269,6 +269,12 @@ assignment to a ``Time`` field:
 In the above example, the value was interpreted as the beginning of today in
 local time, because the application was not configured to use UTC times.
 
+.. note::
+
+  When the database contains a string value for a ``Time`` field, Mongoid
+  parses the string value using ``Time.parse`` which considers values without
+  time zones to be in local time.
+
 
 .. _field-type-date:
 
@@ -295,6 +301,13 @@ recommended to explicitly convert ``String``, ``Time`` and ``DateTime``
 objects to ``Date`` objects before assigning the values to fields of type
 ``Date``.
 
+.. note::
+
+  When the database contains a string value for a ``Date`` field, Mongoid
+  parses the string value using ``Time.parse``, discards the time portion of
+  the resulting ``Time`` object and uses the date portion. ``Time.parse``
+  considers values without time zones to be in local time.
+
 
 .. _field-type-date-time:
 
@@ -364,6 +377,12 @@ If a time zone is specified, it is respected:
     ticket.opened_at
     # => Sun, 04 Mar 2018 09:00:00 +0000
 
+.. note::
+
+  When the database contains a string value for a ``DateTime`` field, Mongoid
+  parses the string value using ``Time.parse`` which considers values without
+  time zones to be in local time.
+
 
 .. _field-type-regexp: