Fix datetimes being incorrectly encoded in frontmatter as strings instead of YAML timestamps

src/writer.js

@@ -81,6 +81,8 @@ async function loadMarkdownFilePromise(post) {
 				// array of one or more strings
 				outputValue = value.reduce((list, item) => `${list}\n  - "${item}"`, '');
 			}
+		} else if (value instanceof luxon.DateTime) {
+			outputValue = encodeDate(value);
 		} else {
 			// single string value
 			const escapedValue = (value || '').replace(/"/g, '\\"');
@@ -98,6 +100,16 @@ async function loadMarkdownFilePromise(post) {
 	return output;
 }
 
+function encodeDate(dateTime) {
+	if (settings.custom_date_formatting) {
+		return dateTime.toFormat(settings.custom_date_formatting);
+	} else if (settings.include_time_with_date) {
+		return dateTime.toISO();
+	} else {
+		return dateTime.toISODate();
+	}
+}
+
 async function writeImageFilesPromise(posts, config) {
 	// collect image data from all posts into a single flattened array of payloads
 	let skipCount = 0;