diff --git a/internal/function_time_parser.go b/internal/function_time_parser.go
index 76781f0..e99ca6f 100644
--- a/internal/function_time_parser.go
+++ b/internal/function_time_parser.go
@@ -873,22 +873,22 @@ func largeAMPMParser(text []rune, t *time.Time) (int, error) {
 	if len(text) < 2 {
 		return progress, fmt.Errorf("cannot parse am/pm format: remaining text [%s]", string(text))
 	}
-	progress += 2
-	toParse := string(text[:progress])
+	toParse := string(text[:2])
 	timeOfDay := strings.ToLower(toParse)
 	if timeOfDay != "am" && timeOfDay != "pm" {
 		return 0, fmt.Errorf("cannot parse am/pm format: [%s] is not am/pm", string(text))
 	}
+	progress += 2
 	return progress, nil
 }
 
 func ampmPostProcessor(text []rune, t *time.Time) {
 	morning := strings.ToLower(string(text)) == "am"
 	hour := t.Hour()
-	if hour == 12 && morning {
-		hour = 0
+	if morning {
+		hour = hour % 12
 	}
-	if !morning {
+	if !morning && hour < 12 {
 		hour += 12
 	}
 	*t = time.Date(
diff --git a/query_test.go b/query_test.go
index 38f49b8..55ffc6e 100644
--- a/query_test.go
+++ b/query_test.go
@@ -4629,11 +4629,11 @@ SELECT date, EXTRACT(ISOYEAR FROM date), EXTRACT(YEAR FROM date), EXTRACT(MONTH
 		},
 		{
 			name:  "parse timestamp with %p",
-			query: `SELECT PARSE_TIMESTAMP("%I%p", "9am"), PARSE_TIMESTAMP("%I%p", "12am"), PARSE_TIMESTAMP("%l%p", " 2am"), PARSE_TIMESTAMP("%I%p", "10PM");`,
+			query: `SELECT PARSE_TIMESTAMP("%I%p", "9am"), PARSE_TIMESTAMP("%I%p", "12am"), PARSE_TIMESTAMP("%l%p", " 12pm"), PARSE_TIMESTAMP("%I%p", "10PM");`,
 			expectedRows: [][]interface{}{{
 				createTimestampFormatFromString("1970-01-01 09:00:00+00"),
 				createTimestampFormatFromString("1970-01-01 00:00:00+00"),
-				createTimestampFormatFromString("1970-01-01 02:00:00+00"),
+				createTimestampFormatFromString("1970-01-01 12:00:00+00"),
 				createTimestampFormatFromString("1970-01-01 22:00:00+00"),
 			}},
 		},