Currently in the settings of an Automation, Communication section, the Time zone Selection only applies to "Wait steps and Time window executions will proceed based on this time zone. "

The time zone selection should also apply to Event Start Dates OR The Event Start Dates Action should give the ability to specify whether the applicable time zone is the Contact's or the Account's time zone.

The Event Start Date says this

"event start date

Use this event to set the Event Start Date to a specific day, date, and/or time, which enables you to use Wait events that hold contacts in relation to the day/date/time that you set"

There is no reference to timezone or ability to specify a timezone

So the current problem this creates is that for business that run event's across multiple timezones, but always want the events to take place at the specified time in the contact's time zone, they have to make adjustments to the actual event start date based on the Account Time Zone (which is what the Event Start Date is based on) and the Contact's Time Zone even though the Automation setting is set to Contact's Timezone