Is there a way to delete all Garmin Connect data before a certain date?

So, here is the way I did it.

1. Go to a daily summary from the past you want to delete.
2. Open your browser's developer tools (in Chrome, right click -> Inspect)
3. Select the network tab in developer tools and clean it
4. No, click on cogwheel in Garmin Connect Web for the daily summary and delete it
5. Look in the developer console for the first request (you should see the date, for example 2014-02-01). Right click on the request, select Copy -> Copy as fetch
6. Take the code below and set your start and end dates for witch you want your daily summaries to be deleted
7. Update the fetch URL as in the example code by removing the date and adding the variable name
8. Copy / paste the code to the browser's JavaScript console and run it

const start = new Date("11/23/2019"); // update this with the first date to delete
const end = new Date("04/20/2020"); // update this with the last date to delete
let loop = new Date(start);
while (loop <= end) {
	let dateString = loop.getFullYear() + "-" + String((loop.getMonth() + 1)).padStart(2, '0') + "-" + String(loop.getDate()).padStart(2, '0');
	console.log("Deleting data for: " + dateString);

	fetch("https://connect.garmin.com/wellness-service/wellness/dailySummary/" + dateString, {
		// removed code for security reasons
		// replace this fetch (...) with ALL the stuff taken from the browsers developer tools with copy -> copy as getch
		// Don't forget to change the URL as in the example above with `+ dateString`
	});

	await new Promise(r => setTimeout(r, 1000));

	let newDate = loop.setDate(loop.getDate() + 1); // DON'T REMOVE THIS. This introduces a one second wait between requests to avoid spamming Garmin servers. We don't to do any harm.
	loop = new Date(newDate);
}

NOTE: Do not refresh the webpage while this code runs!