Refresh the Calendar DOM every minute (#3016)

This keeps relative dates accurate when the calendar's fetch frequency
is much larger than a minute.
As fetching incurs network traffic and load on servers and most
calendars don't update that often, simply refreshing locally is enough.

When using relative for today's events, dates will show as "in X
minutes" or "ends in X minutes" for events within an hour and this goes
out of date quickly. It's weird to see that the time is, say, 16:30 and
an event that you know ends at 16:45 is shown to "ends in 23 minutes"
because that's when the last fetch happened.

Please forgive me if there's style issue, I don't have npm set up on my
machine to run the formatter.

CHANGELOG.md

@@ -26,6 +26,7 @@ _This release is scheduled to be released on 2023-04-01._
 
 - Use develop as target branch for dependabot
 - Update issue template and contributing doc
+- Update dates in Calendar widgets every minute
 
 ### Fixed
 

modules/default/calendar/calendar.js

@@ -86,6 +86,8 @@ Module.register("calendar", {
 
 	// Override start method.
 	start: function () {
+		const ONE_MINUTE = 60 * 1000;
+
 		Log.info("Starting module: " + this.name);
 
 		// Set locale.
@@ -131,6 +133,14 @@ Module.register("calendar", {
 			// fetcher till cycle
 			this.addCalendar(calendar.url, calendar.auth, calendarConfig);
 		});
+
+		// Refresh the DOM every minute if needed: When using relative date format for events that start
+		// or end in less than an hour, the date shows minute granularity and we want to keep that accurate.
+		setTimeout(() => {
+			setInterval(() => {
+				this.updateDom(1);
+			}, ONE_MINUTE);
+		}, ONE_MINUTE - (new Date() % ONE_MINUTE));
 	},
 
 	// Override socket notification handler.