Use BUILD_TIME instead of filestamp of COUNTER for AgeSet and DateSet
--- pym/portage/_sets/dbapi.py
+++ pym/portage/_sets/dbapi.py
@@ -326,6 +326,7 @@
 
 class AgeSet(EverythingSet):
 	_operations = ["merge", "unmerge"]
+	_aux_keys = ('BUILD_TIME',)
 
 	def __init__(self, vardb, mode="older", age=7):
 		super(AgeSet, self).__init__(vardb)
@@ -335,8 +336,11 @@
 	def _filter(self, atom):
 	
 		cpv = self._db.match(atom)[0]
-		path = self._db.getpath(cpv, filename="COUNTER")
-		age = (time.time() - os.stat(path).st_mtime) / (3600 * 24)
+		try:
+			date, = self._db.aux_get(cpv, self._aux_keys)
+		except KeyError:
+			return bool(self._mode == "older")
+		age = (time.time() - float(date)) / (3600 * 24)
 		if ((self._mode == "older" and age <= self._age) \
 			or (self._mode == "newer" and age >= self._age)):
 			return False
@@ -357,6 +361,7 @@
 
 class DateSet(EverythingSet):
 	_operations = ["merge", "unmerge"]
+	_aux_keys = ('BUILD_TIME',)
 
 	def __init__(self, vardb, date, mode="older"):
 		super(DateSet, self).__init__(vardb)
@@ -366,8 +371,10 @@
 	def _filter(self, atom):
 
 		cpv = self._db.match(atom)[0]
-		path = self._db.getpath(cpv, filename="COUNTER")
-		date = os.stat(path).st_mtime
+		try:
+			date, = self._db.aux_get(cpv, self._aux_keys)
+		except KeyError:
+			return bool(self._mode == "older")
 		# Make sure inequality is _strict_ to exclude tested package
 		if ((self._mode == "older" and date < self._date) \
 			or (self._mode == "newer" and date > self._date)):
@@ -402,9 +409,8 @@
 			package = options.get("package")
 			try:
 				cpv = vardbapi.match(package)[0]
-				path = vardbapi.getpath(cpv, filename="COUNTER")
-				date = os.stat(path).st_mtime
-			except ValueError:
+				date, = vardbapi.aux_get(cpv, ('BUILD_TIME',))
+			except KeyError:
 				raise SetConfigError(_("cannot determine installation date of package %s") % package)
 		elif (format == "filestamp"):
 			filestamp = options.get("filestamp")