Shapes and annotations do not handle Date objects or strings with time zones

At the moment (version 1.25.1), data traces can handle Date objects, which will then be displayed with what seems to be the browser's timezone settings. For example, date = new Date("2017-03-30T00:00:00.000Z") used on the X-axis in a trace, with a browser in the UTC+1 timezone will be displayed as "Mar 30, 2017, 01:00", which is indeed correct.

However, that same date object cannot be used for x0/x1 in a shape on the same object.

When using date.toISOString() instead (both for data and shapes), the timezone indicator (e.g. Z) at the end of the string is ignored and the string is considered to be within the local time zone.

Here is a jsfiddle to demonstrate the problem: https://jsfiddle.net/tkhmx8Le/

Effectively, the problem is two-fold (and might lead to two separate issues):

• It would be good if shapes and annotations also supported date objects.
• ISO-8601 date parsing should take into account the Z (or generally +xxxx or +xx:xx) timezone indicator before building its internal UTC representation. This is certainly related to #1003 (and subsequent work).

Start by reproducing the timezone mismatch in the linked JSFiddle, comparing Date objects and ISO-8601 strings in data traces, shapes, and annotations. Read the related work in #1003 and trace the existing date parsing path; done means shapes and annotations accept Date objects and timezone indicators are honored consistently.