Power Automate expressions for beginners

So far you used data as it comes in. With an expression you calculate something with it. You put today's date in front of the name of every attachment your flow saves.

Dynamic content and expressions

Dynamic content is data that an earlier step passes on, such as the name of an attachment. You pick it from a list. An expression is a small formula that calculates something, such as today's date. You type it in the expression editor.

Here is how to get there: click in a field. Two buttons appear next to the field. The lightning bolt opens the list of dynamic content. The fx button opens the expression editor, where you type a formula. Both put the result in the field as a chip.

The result of this lesson: invoice.pdf is saved as 2026-10-04_invoice.pdf. That sorts nicely by date.

Step by step

Open Save attachments via My flows and click Edit. Open the action Create file.
Click in the File Name field, just before the Attachments Name chip. Two buttons appear next to the field.
Click the fx button. A pane opens on the right with the tabs Expression and Dynamic content. Stay on the Expression tab. This is where you type formulas instead of plain text.
Type this in the expression box: convertTimeZone(utcNow(), 'UTC', 'Eastern Standard Time', 'yyyy-MM-dd') and click Add (or Update if you are editing an existing expression). Replace Eastern Standard Time with the name of your own time zone, for example GMT Standard Time or W. Europe Standard Time.
Type the formula on the expression tab. Tap the image to enlarge. It shows the Dutch interface.
Right after the new chip, type an underscore (_), so the date and the name of the attachment are separated.
Save the flow and test it with an email that has a PDF attachment.
Check in OneDrive that the file name starts with today's date, for example 2026-10-04_invoice.pdf.

Why convertTimeZone? The function utcNow() returns the time in UTC. Without converting, the date can be a day off around midnight in your time zone. Error when adding? Check that all brackets and quotation marks match. It is best to copy the formula.

Dynamic content and expressions

Dynamic content and expressions

Step by step

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