One clock for every land: going back to a land catches it up on the time away (like a night's sleep) instead of rewinding to when you left; J3 decided: a server per land with the Valley's as hub, sleep needs everyone in every land

scripts/world/world.gd

@@ -446,6 +446,7 @@ func _on_terrain_ready() -> void:
 		if not state.is_empty():
 			apply_save(state)
 			print("[world] loaded '%s'" % Saves.current_id)
+			catch_up(state.get("catch_up_to", {}))
 		_arrive(Saves.take_arrival(Saves.current_id))
 	player.set_physics_process(true)
 	set_physics_process(true)
@@ -995,6 +996,10 @@ func travel(to: String, arrive: String) -> void:
 	var there: Dictionary = Saves.load_state(id, to)
 	if there.is_empty():
 		there = {"time": here.time}   # (a new place: the same day and hour)
+	else:
+		# One clock for every land: the one you're going to catches up on the
+		# time you were away when it loads (catch_up()).
+		there["catch_up_to"] = here.time
 	there["player"] = here.player
 	Saves.save_state(id, there, 0.0, to)
 	Saves.set_worldlet(id, to, arrive)
@@ -1007,6 +1012,22 @@ func travel(to: String, arrive: String) -> void:
 
 signal travelled(to: String)   ## saved and on the way to another worldlet
 
+## Back in a land you've been to before: its clock comes forward to `to`
+## ({day, time}, the clock where you've come from), and everything in it
+## catches up on the time between, as after a night's sleep (kilns and
+## smelters work, fires burn, food goes off, trees and berries grow back).
+## Returns the seconds caught up.
+func catch_up(to: Dictionary) -> float:
+	if to.is_empty():
+		return 0.0
+	var secs: float = ((int(to.get("day", day_night.day)) - day_night.day) \
+		+ (float(to.get("time", day_night.time)) - day_night.time)) * day_night.day_length
+	if secs <= 0.0:
+		return 0.0
+	skip_time(secs)
+	print("[world] %s caught up on %.0f s while you were away" % [worldlet_id(), secs])
+	return secs
+
 ## Just arrived from another worldlet: put you where you came in.
 func _arrive(at: String) -> void:
 	if at.is_empty():