+sub find_h_unit {
+ my ($class) = @_;
+
+ return $::request->cache('unit_manager')->{h_unit} //= first { $_->name =~ m{^(?: Std | h | Stunde )$}x } @{ $class->all_units };
+}
+
+sub time_based_units {
+ my ($class) = @_;
+
+ my $h_unit = $class->find_h_unit;
+ return [] if !$h_unit;
+ return $::request->cache('unit_manager')->{units} //= $h_unit->convertible_units;
+}
+