diff --git a/lib/std/time/datetime.c3 b/lib/std/time/datetime.c3
index 3c5ee9c5d..060cc2248 100644
--- a/lib/std/time/datetime.c3
+++ b/lib/std/time/datetime.c3
@@ -46,7 +46,7 @@ fn TzDateTime DateTime.to_local(&self)
 	dt.day = (char)tm.tm_mday;
 	dt.month = (Month)tm.tm_mon;
 	dt.year = tm.tm_year + 1900;
-	dt.weekday = !tm.tm_wday ? Weekday.SUNDAY : (Weekday)tm.tm_wday + 1;
+	dt.weekday = !tm.tm_wday ? Weekday.SUNDAY : (Weekday)tm.tm_wday - 1;
 	dt.year_day = (ushort)tm.tm_yday;
 	dt.time = self.time;
 	$if $defined(tm.tm_gmtoff):
@@ -144,7 +144,7 @@ fn void DateTime.set_time(&self, Time time)
 	self.day = (char)tm.tm_mday;
 	self.month = (Month)tm.tm_mon;
 	self.year = tm.tm_year + 1900;
-	self.weekday = !tm.tm_wday ? Weekday.SUNDAY : (Weekday)tm.tm_wday + 1;
+	self.weekday = !tm.tm_wday ? Weekday.SUNDAY : (Weekday)tm.tm_wday - 1;
 	self.year_day = (ushort)tm.tm_yday;
 	self.time = time;
 }