diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala
index 6800abb2ae109..949e857aa8fc7 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/DateTimeUtils.scala
@@ -337,7 +337,9 @@ object DateTimeUtils {
 
   def microsToInstant(us: Long): Instant = {
     val secs = Math.floorDiv(us, MICROS_PER_SECOND)
-    val mos = Math.floorMod(us, MICROS_PER_SECOND)
+    // Unfolded Math.floorMod(us, MICROS_PER_SECOND) to reuse the result of
+    // the above calculation of `secs` via `floorDiv`.
+    val mos = us - secs * MICROS_PER_SECOND
     Instant.ofEpochSecond(secs, mos * NANOS_PER_MICROS)
   }
 
@@ -691,11 +693,11 @@ object DateTimeUtils {
   def truncDate(d: SQLDate, level: Int): SQLDate = {
     def truncToYearLevel(divider: Int, adjust: Int): SQLDate = {
       val oldYear = getYear(d)
-      var newYear = Math.floorDiv(oldYear, divider)
-      if (adjust > 0 && Math.floorMod(oldYear, divider) == 0) {
-        newYear -= 1
+      var newYear = Math.floorDiv(oldYear, divider) * divider
+      if (adjust > 0 && newYear == oldYear) {
+        newYear -= divider
       }
-      newYear = newYear * divider + adjust
+      newYear += adjust
       localDateToDays(LocalDate.of(newYear, 1, 1))
     }
     level match {