I am not 100% understanding what you are looking to accomplish. But, SharePoint stores all dates in UTC even when you set a different time zone at the site level. Users should specify their time zone in their user profile, which will then adjust the UTC stored value to their time zone.
If you need to convert this in a workflow to send data to the users, you can use a Graph API request to get their time zone value and adjust it with the Convert time zone action. I think if you modify the time how you propose, this will just throw off the date/time for people who have correctly set up their user profile.
The flow would look like this:
This is the scheme for the Parse JSON action and what is returned:
{
"type": "object",
"properties": {
"@@odata.context": {
"type": "string"
},
"archiveFolder": {
"type": "string"
},
"timeZone": {
"type": "string"
},
"delegateMeetingMessageDeliveryOptions": {
"type": "string"
},
"dateFormat": {
"type": "string"
},
"timeFormat": {
"type": "string"
},
"userPurpose": {
"type": "string"
},
"automaticRepliesSetting": {
"type": "object",
"properties": {
"status": {
"type": "string"
},
"externalAudience": {
"type": "string"
},
"internalReplyMessage": {
"type": "string"
},
"externalReplyMessage": {
"type": "string"
},
"scheduledStartDateTime": {
"type": "object",
"properties": {
"dateTime": {
"type": "string"
},
"timeZone": {
"type": "string"
}
}
},
"scheduledEndDateTime": {
"type": "object",
"properties": {
"dateTime": {
"type": "string"
},
"timeZone": {
"type": "string"
}
}
}
}
},
"language": {
"type": "object",
"properties": {
"locale": {
"type": "string"
},
"displayName": {
"type": "string"
}
}
},
"workingHours": {
"type": "object",
"properties": {
"daysOfWeek": {
"type": "array",
"items": {
"type": "string"
}
},
"startTime": {
"type": "string"
},
"endTime": {
"type": "string"
},
"timeZone": {
"type": "object",
"properties": {
"name": {
"type": "string"
}
}
}
}
}
}
}