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).

Inizia riproducendo la discrepanza di fuso orario nel JSFiddle collegato, confrontando gli oggetti Date e le stringhe ISO-8601 in data traces, shapes e annotations. Leggi il lavoro correlato in #1003 e traccia il percorso esistente per l’analisi delle date; il lavoro è completato quando shapes e annotations accettano oggetti Date e gli indicatori di fuso orario vengono rispettati in modo coerente.