I made an example flow that hopefully will give an example of what to do with dates and times. Fortunately, daylight savings time is next week, so my example will cross the time change.
I'm in U.S. Central Time zone so I had to keep it like that for the example to reflect appropriately. You will just need to change this to your local timezone to work for you.
I have a single SharePoint list that I will use for this example just to keep it simple. There is an item with a Start Time that is written in a single line text column in the format of 5:00 PM. There is a Start Date column that is a date time type column which only has the date value with the date as 11/2/2023. (The sharepoint list display format of a date value is MM/dd/yyyy but the time is stored in the system as ISO 8601 yyyy-MM-dd.)
There is a third column that is a date time type column which has both date and time. I will update the item with the combined Date and text time value.
SP List Item with a text time and a date column
SP List Settings to see the column types.
I have an example flow that is going to do two things.
Scope A - The flow is going to get an item that has a text time value and a date value and put them together into a SharePoint datetime type column. So this will be a single item that has a usable datetime value.
Scope B - This part of the flow is going to use the first item and add 6 days to it and create a new item (in the same list.)
Flow overview - Scope A will update the current item - Scope B will create a new item.
The first thing that needs to be done is to combine the text time with the date value. This needs to stay in the local timezone. Put the dynamic content of the StartDate with a space followed by the StartTime. Power Automate will be able to read this datetime time format.
A1 - This is just to get the date and time into the ISO 8601 format so that it can be used in other steps. It is not converting the time zone, it is using the same timezone as the source and destination. (Be sure to use the [s] sortable format string. DO NOT USE [u] universal.)
A2 - This will convert the local time into the UTC timezone in order to fill the date and time column for the current item. This will use the outputs of A1 as the source time. It will convert it from Local to UTC. (Be sure to use the [u] universal format string. If a time ends with Z it is in UTC timezone.)
This scope will update the item with a date and time
A1 uses the Convert Time Zone to correctly format the date and time - do not change the timezone
A2 uses the output of local time from A1 to convert to UTC timezone and then updates the item.
The second scope of the flow is an example of creating a new item. This will use the outputs of the A1 local timezone to add days. Once the days are added, then it will be converted to UTC in order to populate the date and time column in the SharePoint list.
B1 - Add to Time - this will add days to the output of A1 Local Formatted Date Time and will remain in the local timezone
B2 - This will convert the new time of the event from Local to UTC.
The individual time text column will use the output of the Add to Time action with the formatDateTime() function which just shows the hours. The individual date column will use the output of the Add to Time action with the formatDateTime() function which just has the date.
Scope B - creates a new event with time added to the original local time of the event
Zoom Scope B - actions B1 will add to the original local time and B2 will convert to UTC
Create new item uses the outputs from B1 and B2 to populate the individual fields.
If I run the flow using my original item from the SharePoint list, I get these results.
Results Scope A
Zoom Results Scope A
Results Scope B
Zoom Results Scope B
Initial Item Before Flow
Updated Item and Created Item
I hope these examples help you with getting your flow put together. I added a lot of photos so it might be easier to see what is happening and if you are getting errors double check the details.
Let me know if this works for you