diff --git a/client_src/css/popup.css b/client_src/css/popup.css
index f12fc78..1f3fc83 100644
--- a/client_src/css/popup.css
+++ b/client_src/css/popup.css
@@ -4,7 +4,7 @@
 
 h2.device-name { text-align: center; }
 .device-name::after {
-	content: "#" attr(data-id);
+	content: "#" attr(data-id) ", " attr(data-minutes_ago);
 	float: right; margin-right: 1em;
 	
 	font-size: 80%;
diff --git a/client_src/js/DeviceData.mjs b/client_src/js/DeviceData.mjs
index c0bb8e2..3a4c8ae 100644
--- a/client_src/js/DeviceData.mjs
+++ b/client_src/js/DeviceData.mjs
@@ -26,8 +26,12 @@ class DeviceData {
 		
 		// Create a map to help us lookup ids faster
 		this.device_map = new Map();
-		for(let device of this.devices)
+		for(let device of this.devices) {
+			// Parse the last_seen date into a JS date object
+			device.last_seen = new Date(device.last_seen);
+			// Add the device to the device map
 			this.device_map.set(device.id, device);
+		}
 	}
 	
 	/**
diff --git a/client_src/js/Helpers/DateHelper.mjs b/client_src/js/Helpers/DateHelper.mjs
index 470e16c..0669fbf 100644
--- a/client_src/js/Helpers/DateHelper.mjs
+++ b/client_src/js/Helpers/DateHelper.mjs
@@ -10,4 +10,43 @@ function human_duration_unit(milliseconds) {
 	return "year";
 }
 
-export { human_duration_unit };
+/**
+ * Calculates the time since a particular datetime and returns a
+ * human-readable result.
+ * @source Ported from PHP in Pepperminty Wiki	https://github.com/sbrl/Pepperminty-Wiki/blob/712e954/core/05-functions.php#L55-L89
+ * @param	{Date}		datetime	The datetime to convert.
+ * @return	{string}	The time since the given timestamp as a human-readable string.
+ */
+function human_time_since(datetime) {
+	return human_time((new Date() - datetime) / 1000);
+}
+/**
+ * Renders a given number of seconds as something that humans can understand more easily.
+ * @source Ported from PHP in Pepperminty Wiki	https://github.com/sbrl/Pepperminty-Wiki/blob/712e954/core/05-functions.php#L55-L89
+ * @param 	{int}		seconds	The number of seconds to render.
+ * @return	{string}	The rendered time.
+ */
+function human_time(seconds)
+{
+	if(seconds < 0) return "the future";
+	
+	let tokens = new Map([
+		[ 31536000, 'year' ],
+		[ 2592000, 'month' ],
+		[ 604800, 'week' ],
+		[ 86400, 'day' ],
+		[ 3600, 'hour' ],
+		[ 60, 'minute' ],
+		[ 1, 'second' ]
+	]);
+	for(let unit of tokens) {
+		if (seconds < unit[0]) continue;
+		numberOfUnits = Math.floor(seconds / unit[0]);
+		return `${numberOfUnits} ${unit[1]}${((numberOfUnits > 1)?'s':'')} ago`;
+	}
+}
+
+export {
+	human_duration_unit,
+	human_time_since, human_time
+};
diff --git a/client_src/js/LayerDeviceMarkers.mjs b/client_src/js/LayerDeviceMarkers.mjs
index 11f2a1b..1cc4eb9 100644
--- a/client_src/js/LayerDeviceMarkers.mjs
+++ b/client_src/js/LayerDeviceMarkers.mjs
@@ -11,6 +11,7 @@ import Emitter from 'event-emitter-es6';
 import Config from './Config.mjs';
 import DeviceReadingDisplay from './DeviceReadingDisplay.mjs';
 import GetFromUrl from './Helpers/GetFromUrl.mjs';
+import { human_time_since } from './Helpers/DateHelper.mjs';
 
 class LayerDeviceMarkers extends Emitter {
 	constructor(in_map, in_device_data) {
@@ -70,6 +71,7 @@ class LayerDeviceMarkers extends Emitter {
 		console.info("Fetching device info for device", device_id);
 		let device_info = JSON.parse(await GetFromUrl(`${Config.api_root}?action=device-info&device-id=${device_id}`));
 		
+		device_info.last_seen = new Date(`${device_info.last_seen}+0000`); // Force parsing as UTC
 		device_info.location = [ device_info.latitude, device_info.longitude ];
 		delete device_info.latitude;
 		delete device_info.longitude;
@@ -88,6 +90,8 @@ class LayerDeviceMarkers extends Emitter {
 			`Device: ${device_info.name}`
 		));
 		result.querySelector(".device-name").dataset.id = device_info.id;
+		result.querySelector(".device-name").dataset.last_seen = device_info.last_seen;
+		result.querySelector(".device-name").dataset.minutes_ago = human_time_since(device_info.last_seen);
 		
 		
 		// ----------------------------------