diff --git a/core/time/datetime/datetime.odin b/core/time/datetime/datetime.odin
index e15ced5a5..89fa2ce98 100644
--- a/core/time/datetime/datetime.odin
+++ b/core/time/datetime/datetime.odin
@@ -127,13 +127,13 @@ days_remaining :: proc "contextless" (date: Date) -> (days_remaining: i64, err:
 	return delta.days, .None
 }
 
-last_day_of_month :: proc "contextless" (#any_int year: i64, #any_int month: i8) -> (day: i64, err: Error) {
+last_day_of_month :: proc "contextless" (#any_int year: i64, #any_int month: i8) -> (day: i8, err: Error) {
 	// Not using formula 2.27 from the book. This is far simpler and gives the same answer.
 
 	validate(Date{year, month, 1}) or_return
 	month_days := MONTH_DAYS
 
-	day = i64(month_days[month])
+	day = month_days[month]
 	if month == 2 && is_leap_year(year) {
 		day += 1
 	}