Option expirations read as midnight in the server's time zone, not US/Eastern: Carbon::parse without a zone #103

What happens

An option expiration comes back as midnight in the server's PHP time zone instead of midnight in US/Eastern. With the default date.timezone (UTC), the expiration 2026-09-23 is 2026-09-23 00:00:00 UTC, which is 2026-09-22 20:00 -04:00 in New York: the evening before. On a server set to another zone it is yet another instant, so the value depends on the host.

The same expiration under dateformat=unix is 1790136000, 2026-09-23 04:00:00 UTC: midnight in New York. The two readings are four hours apart (five in winter).

Why

The API writes a date as %Y-%m-%d, meaning that calendar day in US/Eastern (marketDataApi/common/util/date_helper.py::DateHelper.format_date). JSON requests from this SDK send no dateformat (DateFormat applies to CSV only), and on the default format the API sends the expirations of options/expirations as dates. Measured live on 2026-09-22: GET /v1/options/expirations/AAPL/ returned "expirations": ["2026-09-23", …] beside a Unix updated.

Expirations builds each value with Carbon::parse($expiration) and no time zone (L75 for the human-readable format, L85 for the regular one, at ec5181b). A string without a zone takes date_default_timezone_get(). tests/Unit/Options/ExpirationsTest.php compares the result with Carbon::parse('2022-09-23') in that same default zone, so it cannot see the difference.

date_default_timezone_set('UTC');
$expiration = Carbon\Carbon::parse('2026-09-23');
echo $expiration->setTimezone('America/New_York')->toIso8601String(); // 2026-09-22T20:00:00-04:00

Candles, earnings, news, market status and fund candles read their dates with the same Carbon::parse call, so any date-only value they receive reads the same way. Those were not measured here.

Definition of done

• A date the API sends without a time is midnight America/New_York of that date, whatever the server's date.timezone.
• Tests that set a default zone other than US/Eastern and assert the wall-clock time and the offset, not equality with another Carbon::parse.

Found while fixing the same defect in the C# SDK (MarketDataApp/sdk-csharp#111, fixed in MarketDataApp/sdk-csharp#114). The Python SDK tracks it in MarketDataApp/sdk-py#143.