add feature to customize date formatting

src/utils/DateFormatter.ts

@@ -0,0 +1,70 @@
+// obsidian already uses moment, so no need to package it twice!
+// import { moment } from 'obsidian'; // doesn't work for release build
+// obsidian uses a namespace-style import for moment, which ES6 doesn't allow anymore
+const obsidian = require('obsidian');
+const moment = obsidian.moment;
+
+export class DateFormatter {
+	toFormat: string;
+	localeString: string;
+
+	constructor() {
+		this.toFormat = 'YYYY-MM-DD';
+		// get locale string (e.g. en, en-gb, de, fr, etc.)
+		this.localeString = new Intl.DateTimeFormat().resolvedOptions().locale;
+	}
+
+	setFormat(format: string): void {
+		this.toFormat = format;
+	}
+
+	getPreview(format?: string): string {
+		const today = moment();
+		today.locale(this.localeString);
+
+		if (!format) {
+			format = this.toFormat;
+		}
+
+		return today.format(format);
+	}
+
+	/**
+	 * Tries to format a given date string with the currently set date format.
+	 * You can set a date format by calling `setFormat()`.
+	 *
+	 * @param dateString the date string to be formatted
+	 * @param dateFormat the current format of `dateString`. When this is `null` and the actual format of the 
+	 * given date string is not `C2822` or `ISO` format, this function will try to guess the format by using the native `Date` module.
+	 * @returns formatted date string or null if `dateString` is not a valid date
+	 */
+	format(dateString: string, dateFormat?: string): string | null {
+		if (!dateString) {
+			return null;
+		}
+
+		let date: moment.Moment;
+
+		if (!dateFormat) {
+			// reading date formats other then C2822 or ISO with moment is deprecated
+			if (this.hasMomentFormat(dateString)) {
+				// expect C2822 or ISO format
+				date = moment(dateString);
+			} else {
+				// try to read date string with native Date
+				date = moment(new Date(dateString));
+			}
+			date.locale(this.localeString); // set local locale definition for moment
+		} else {
+			date = moment(dateString, dateFormat, this.localeString);
+		}
+
+		// format date (if it is valid)
+		return date.isValid() ? date.format(this.toFormat) : null;
+	}
+
+	private hasMomentFormat(dateString: string): boolean {
+		const date = moment(dateString, true); // strict mode
+		return date.isValid();
+	}
+}

src/utils/Utils.ts

@@ -135,6 +135,8 @@ export function markdownTable(content: string[][]): string {
 	return table;
 }
 
+export const fragWithHTML = (html: string) => createFragment(frag => (frag.createDiv().innerHTML = html));
+
 export function dateToString(date: Date): string {
 	return `${date.getMonth() + 1}-${date.getDate()}-${date.getFullYear()}`;
 }