You can do this directly in Ads Editor, even while the ad set or campaign is active.

On screen: in Meta Ads, select the campaigns (or ad sets) you want to change. In the bulk edit bar that appears at the bottom, click End Date (for campaigns, the button is next to Edit Name; for ad sets, it's inside the Edit Set menu). Choose the Date and Time and click Save. The time uses the ad account's time zone. You can change one item or several at once. If only one is selected, the window shows its current end date.

To remove the end date, open the same option and select No end date (continues running). An ad set or campaign with a lifetime budget must have an end date, so Meta doesn't allow removing it in that case.

You can also do it through AI Copilot or MCP: ask, for example, "end ad set X on the 7th" or "remove the end date from campaign Y" (the tool is `set_end_date`). If your ChatGPT or Claude doesn't show this function, start a new conversation: the MCP function list is loaded at the start of each conversation.