diff --git a/include/tz_database.hrl b/include/tz_database.hrl
index 48a2a33..c4a0c6d 100644
--- a/include/tz_database.hrl
+++ b/include/tz_database.hrl
@@ -23,7 +23,7 @@
 %   StdMin = Integer(), GMT offset in minutes. W/o daylight savings
 %   DstMin = Integer(), daylight saving. Adjustment for GMT offset, when daylight saving is on
 %   DstStartDay = {NthWeekday, Weekday, Month}, daylight saving transition rule. Can be undef if no daylight saving rule specified
-%     NthWeekday = Integer(), 1(first week),2(second week),3(...),4(...),5(...),-1(last week)
+%     NthWeekday = Integer() | 'last', 1(first week),2(second week),3(...),4(...),5(...),'last'(last week)
 %     Weekday = atom(),  sun,mon,tue,wed,thu,fri,sat
 %     Month = atom(),  jan,deb,mar,apr,may,jun,jul,aug,sep,oct,mov,dec
 %   DstStartTime = {Hour, Min} - time of daylight saving transition