Index: binaries/data/mods/public/gui/common/functions_utility.js
===================================================================
--- binaries/data/mods/public/gui/common/functions_utility.js
+++ binaries/data/mods/public/gui/common/functions_utility.js
@@ -109,14 +109,33 @@
 }
 
 /**
- * Convert time in milliseconds to [hh:]mm:ss string representation.
+ * Convert time in milliseconds to m:ss or H:mm:ss string representation.
  * @param time Time period in milliseconds (integer)
  * @return String representing time period
  */
 function timeToString(time)
 {
 	return Engine.FormatMillisecondsIntoDateStringGMT(time, time < 1000 * 60 * 60 ?
-		translate("mm:ss") : translate("HH:mm:ss"));
+		// Translation: Format of the time elapsed or remaining, for game durations, ceasefire and wonder-victory countdowns, etc.
+		// For a list of symbols that you can use, see:
+		// https://sites.google.com/site/icuprojectuserguide/formatparse/datetime?pli=1#TOC-Date-Field-Symbol-Table
+		translateWithContext("countdown format for times less than one hour", "m:ss") :
+		// Translation: Format of the time elapsed or remaining, for game durations, ceasefire and wonder-victory countdowns, etc.
+		// For a list of symbols that you can use, see:
+		// https://sites.google.com/site/icuprojectuserguide/formatparse/datetime?pli=1#TOC-Date-Field-Symbol-Table
+		translateWithContext("countdown format for times greater than one hour", "H:mm:ss"));
+}
+
+function chatTimestampToString(time)
+{
+	return sprintf(
+		// Translation: Time prefix as shown in the chat in the lobby, game setup, and session (when you enable it in the options page).
+		translate("\\[%(time)s]"), {
+			// Translation: Format of the local time as shown in the chat in the lobby, game setup, and session (when you enable it in the options page).
+			// For a list of symbols that you can use, see:
+			// https://sites.google.com/site/icuprojectuserguide/formatparse/datetime?pli=1#TOC-Date-Field-Symbol-Table
+			"time": Engine.FormatMillisecondsIntoDateStringLocal(time, translateWithContext("chat timestamp format", "HH:mm"))
+		});
 }
 
 function removeDupes(array)
Index: binaries/data/mods/public/gui/common/functions_utility_loadsave.js
===================================================================
--- binaries/data/mods/public/gui/common/functions_utility_loadsave.js
+++ binaries/data/mods/public/gui/common/functions_utility_loadsave.js
@@ -12,7 +12,10 @@
 function generateSavegameDateString(metadata, engineInfo)
 {
 	return compatibilityColor(
-		Engine.FormatMillisecondsIntoDateStringLocal(metadata.time * 1000, translate("yyyy-MM-dd HH:mm:ss")),
+		// Translation: Format of the local time as shown in the load game menu and the save game dialog.
+		// For a list of symbols that you can use, see:
+		// https://sites.google.com/site/icuprojectuserguide/formatparse/datetime?pli=1#TOC-Date-Field-Symbol-Table
+		Engine.FormatMillisecondsIntoDateStringLocal(metadata.time * 1000, translateWithContext("load/save game date format", "yyyy-MM-dd HH:mm:ss")),
 		isCompatibleSavegame(metadata, engineInfo));
 }
 
Index: binaries/data/mods/public/gui/gamesetup/gamesetup.js
===================================================================
--- binaries/data/mods/public/gui/gamesetup/gamesetup.js
+++ binaries/data/mods/public/gui/gamesetup/gamesetup.js
@@ -2151,9 +2151,7 @@
 
 	if (Engine.ConfigDB_GetValue("user", "chat.timestamp") == "true")
 		text = sprintf(translate("%(time)s %(message)s"), {
-			"time": sprintf(translate("\\[%(time)s]"), {
-				"time": Engine.FormatMillisecondsIntoDateStringLocal(Date.now(), translate("HH:mm"))
-			}),
+			"time": chatTimestampToString(Date.now()),
 			"message": text
 		});
 
Index: binaries/data/mods/public/gui/lobby/lobby.js
===================================================================
--- binaries/data/mods/public/gui/lobby/lobby.js
+++ binaries/data/mods/public/gui/lobby/lobby.js
@@ -994,9 +994,11 @@
 	sgGameStartTime.hidden = !game.startTime;
 	if (game.startTime)
 		sgGameStartTime.caption = sprintf(
-			// Translation: %(time)s is the hour and minute here.
 			translate("Game started at %(time)s"), {
-				"time": Engine.FormatMillisecondsIntoDateStringLocal(+game.startTime*1000, translate("HH:mm"))
+				// Translation: Format of the local start time of a selected game in the lobby.
+				// For a list of symbols that you can use, see:
+				// https://sites.google.com/site/icuprojectuserguide/formatparse/datetime?pli=1#TOC-Date-Field-Symbol-Table
+				"time": Engine.FormatMillisecondsIntoDateStringLocal(game.startTime * 1000, translateWithContext("game start time format", "HH:mm"))
 			});
 
 	sgNbPlayers.caption = sprintf(
@@ -1348,19 +1350,9 @@
 	if (Engine.ConfigDB_GetValue("user", "chat.timestamp") != "true")
 		return formattedMessage;
 
-	// Translation: Time as shown in the multiplayer lobby (when you enable it in the options page).
-	// For a list of symbols that you can use, see:
-	// https://sites.google.com/site/icuprojectuserguide/formatparse/datetime?pli=1#TOC-Date-Field-Symbol-Table
-	let timeString = Engine.FormatMillisecondsIntoDateStringLocal(msg.time ? msg.time * 1000 : Date.now(), translate("HH:mm"));
-
-	// Translation: Time prefix as shown in the multiplayer lobby (when you enable it in the options page).
-	let timePrefixString = sprintf(translate("\\[%(time)s]"), {
-		"time": timeString
-	});
-
 	// Translation: IRC message format when there is a time prefix.
 	return sprintf(translate("%(time)s %(message)s"), {
-		"time": senderFont(timePrefixString),
+		"time": senderFont(chatTimestampToString(msg.time ? msg.time * 1000 : Date.now())),
 		"message": formattedMessage
 	});
  }
Index: binaries/data/mods/public/gui/replaymenu/replay_menu.js
===================================================================
--- binaries/data/mods/public/gui/replaymenu/replay_menu.js
+++ binaries/data/mods/public/gui/replaymenu/replay_menu.js
@@ -296,7 +296,10 @@
  */
 function getReplayDateTime(replay)
 {
-	return Engine.FormatMillisecondsIntoDateStringLocal(replay.attribs.timestamp * 1000, translate("yyyy-MM-dd HH:mm"));
+	// Translation: Format of the local time as shown in the replay menu.
+	// For a list of symbols that you can use, see:
+	// https://sites.google.com/site/icuprojectuserguide/formatparse/datetime?pli=1#TOC-Date-Field-Symbol-Table
+	return Engine.FormatMillisecondsIntoDateStringLocal(replay.attribs.timestamp * 1000, translateWithContext("replay date format", "yyyy-MM-dd HH:mm"));
 }
 
 /**
@@ -326,11 +329,14 @@
  */
 function getReplayMonth(replay)
 {
-	return Engine.FormatMillisecondsIntoDateStringLocal(replay.attribs.timestamp * 1000, translate("yyyy-MM"));
+	// Translation: Format of the local time (month) as shown in the date filter dropdown in the replay menu.
+	// For a list of symbols that you can use, see:
+	// https://sites.google.com/site/icuprojectuserguide/formatparse/datetime?pli=1#TOC-Date-Field-Symbol-Table
+	return Engine.FormatMillisecondsIntoDateStringLocal(replay.attribs.timestamp * 1000, translateWithContext("replay date filter format", "yyyy-MM"));
 }
 
 /**
- * Returns a human-readable version of the time when the replay started.
+ * Returns a human-readable version of the duration of the replay.
  *
  * @returns {string}
  */
Index: binaries/data/mods/public/gui/session/messages.js
===================================================================
--- binaries/data/mods/public/gui/session/messages.js
+++ binaries/data/mods/public/gui/session/messages.js
@@ -894,9 +894,7 @@
 	// Save to chat history
 	let historical = {
 		"txt": formatted,
-		"timePrefix": sprintf(translate("\\[%(time)s]"), {
-			"time": Engine.FormatMillisecondsIntoDateStringLocal(Date.now(), translate("HH:mm"))
-		}),
+		"timePrefix": chatTimestampToString(Date.now()),
 		"filter": {}
 	};
 
Index: binaries/data/mods/public/gui/session/selection_panels.js
===================================================================
--- binaries/data/mods/public/gui/session/selection_panels.js
+++ binaries/data/mods/public/gui/session/selection_panels.js
@@ -639,7 +639,7 @@
 
 		// Show the time remaining to finish the first item
 		if (data.i == 0)
-			Engine.GetGUIObjectByName("queueTimeRemaining").caption = Engine.FormatMillisecondsIntoDateStringGMT(data.item.timeRemaining, translateWithContext("countdown format", "m:ss"));
+			Engine.GetGUIObjectByName("queueTimeRemaining").caption = timeToString(data.item.timeRemaining);
 
 		let guiObject = Engine.GetGUIObjectByName("unitQueueProgressSlider["+data.i+"]");
 		let size = guiObject.size;