Because mobile and browser users move between time zones as they create data, the nature of data in or age is that each row of a table can be collected in a different time zone. Because storing all dates as UTC is not always desirable, I suggest ESRI support the various date time data types that are time zone aware so that each date value in a row can know what time zone it was collected in. Time zone aware data types already exists in Oracle, SQL Server , PostgreSQL and I suspect other RDMS that the Geodatabase supports.
Sql Server: datetimeoffset (Transact-SQL)
Oracle: Datetime Datatypes and Time Zone Support ),
PostgreSQL: PostgreSQL: Documentation: 8.2: Date/Time Types