From a purely technical perspective, locales and cultures have no bearing on timezones (i.e., en-US does not mean or even imply the EST time zone, or any other time zone). This is not a Sitecore specific detail.

Inside the CMS, dates are displayed and take input based on the ServerTimeZone setting. However, all dates are stored inside the database as UTC and retrieved as UTC.

The language version of an item has no bearing on what time zone the date/time field is using for input. If you want the ability to set specific time zones on date fields, you'll need to use a custom field such as this one: CustomDateTimeZone

From a purely technical perspective, locales and cultures have no bearing on timezones (i.e., en-US does not mean or even imply the EST time zone, or any other time zone). This is not a Sitecore specific detail.

Inside the CMS, dates are displayed and take input based on the ServerTimeZone setting. However, all dates are stored inside the database as UTC and retrieved as UTC.

The language version of an item has no bearing on what time zone the date/time field is using for input. If you want the ability to set specific time zones on date fields, you'll need to use a custom field such as this one: DateTimeZoneField