Create timestamp in Sharepoint

Rob Nunley  Yes this is possible. First make sure that versioning is turned on in List Settings as the flow compares the current version with the previous one to see if the Completed column has changed.

1. The trigger is a SharePoint When an item or a file is modified:

Once you have selected your site and list you need to add trigger conditions so that you don't end up in an infinite loop. So click the 3 dots at the top right of the action and select Settings. At the bottom of the panel that appears you add the following 2 trigger conditions:

@equals(triggerBody()?['Completed'],true)
@empty(triggerBody()?['TimeCompleted'])

What this does is to trigger the flow only if the Completed column has a Yes in it and if the TimeCompleted column is empty:

Next, we want to get the changes that have happened, so add a Get Changes for an item or a file (properties only) action. In the Since field select Trigger Window Start Token and in the Until field select Trigger Window End Token:

Next, I want the flow to add the data into the TimeCompleted column in a specific format, so I've added a Compose control and in the inputs added the following expression: 

(the capital Hs are to use the 24-hour time).

Next we want to check if specifically the Completed column has changed. Add a Condition and select Has Column Changed: Completed from the dynamic content, in the middle field select is equal to and in the right field type true

As this is a Condition you'll have the normal green If yes channel and the Red If no channel. You don't want anything to happen in the red channel so leave it empty. But in the green channel add a SharePoint Update item action. Select the site and list from the dropdowns and the ID and Title from the dynamic content box. In the TimeCompleted field select the outputs from the Compose control.

When a user changes the Completed column in the SharePoint list to yes the flow  will run and add today's date and time into the TimeCompleted column. It might take a minute or 2 to do it but you can see it happening in the attached video.

Rob
Los Gallardos
Microsoft Power Automate Community Super User