diff --git a/generic/tclClock.c b/generic/tclClock.c
index 113a5d2..fdaa2d4 100644
--- a/generic/tclClock.c
+++ b/generic/tclClock.c
@@ -3777,13 +3777,19 @@ ClockScanCommit(
 	}
     }
 
+    /* If seconds overflows the day (no validate case), increase days */
+    if (yySecondOfDay >= SECONDS_PER_DAY) {
+	yydate.julianDay += (yySecondOfDay / SECONDS_PER_DAY);
+	yySecondOfDay %= SECONDS_PER_DAY;
+    }
+
     /* Local seconds to UTC (stored in yydate.seconds) */
 
     if (info->flags & (CLF_ASSEMBLE_SECONDS)) {
 	yydate.localSeconds =
-	    -210866803200L
-	    + ( SECONDS_PER_DAY * (Tcl_WideInt)yydate.julianDay )
-	    + ( yySecondOfDay % SECONDS_PER_DAY );
+		-210866803200LL
+		+ (SECONDS_PER_DAY * yydate.julianDay)
+		+ yySecondOfDay;
     }
 
     if (info->flags & (CLF_ASSEMBLE_SECONDS|CLF_LOCALSEC)) {
diff --git a/generic/tclClockFmt.c b/generic/tclClockFmt.c
index 4c37ee3..1af0c68 100644
--- a/generic/tclClockFmt.c
+++ b/generic/tclClockFmt.c
@@ -1735,7 +1735,7 @@ ClockScnToken_JDN_Proc(ClockFmtScnCmdArgs *opts,
 
     fractJD = (int)tok->map->offs /* 0 for calendar or 43200 for astro JD */
 	+ (int)((Tcl_WideInt)SECONDS_PER_DAY * fractJD / fractJDDiv);
-    if (fractJD > SECONDS_PER_DAY) {
+    if (fractJD >= SECONDS_PER_DAY) {
 	fractJD %= SECONDS_PER_DAY;
 	intJD += 1;
     }
diff --git a/generic/tclDate.c b/generic/tclDate.c
index 4b09954..f9d8dbc 100644
--- a/generic/tclDate.c
+++ b/generic/tclDate.c
@@ -2360,24 +2360,12 @@ ToSeconds(
     int Seconds,
     MERIDIAN Meridian)
 {
-    if (Minutes < 0 || Minutes > 59 || Seconds < 0 || Seconds > 59) {
-	return -1;
-    }
     switch (Meridian) {
     case MER24:
-	if (Hours < 0 || Hours > 23) {
-	    return -1;
-	}
 	return (Hours * 60 + Minutes) * 60 + Seconds;
     case MERam:
-	if (Hours < 1 || Hours > 12) {
-	    return -1;
-	}
 	return ((Hours % 12) * 60 + Minutes) * 60 + Seconds;
     case MERpm:
-	if (Hours < 1 || Hours > 12) {
-	    return -1;
-	}
 	return (((Hours % 12) + 12) * 60 + Minutes) * 60 + Seconds;
     }
     return -1;			/* Should never be reached */
diff --git a/generic/tclGetDate.y b/generic/tclGetDate.y
index 89ccd24..d001155 100644
--- a/generic/tclGetDate.y
+++ b/generic/tclGetDate.y
@@ -730,24 +730,12 @@ ToSeconds(
     int Seconds,
     MERIDIAN Meridian)
 {
-    if (Minutes < 0 || Minutes > 59 || Seconds < 0 || Seconds > 59) {
-	return -1;
-    }
     switch (Meridian) {
     case MER24:
-	if (Hours < 0 || Hours > 23) {
-	    return -1;
-	}
 	return (Hours * 60 + Minutes) * 60 + Seconds;
     case MERam:
-	if (Hours < 1 || Hours > 12) {
-	    return -1;
-	}
 	return ((Hours % 12) * 60 + Minutes) * 60 + Seconds;
     case MERpm:
-	if (Hours < 1 || Hours > 12) {
-	    return -1;
-	}
 	return (((Hours % 12) + 12) * 60 + Minutes) * 60 + Seconds;
     }
     return -1;			/* Should never be reached */
diff --git a/tests/clock.test b/tests/clock.test
index bf48516..84e933f 100644
--- a/tests/clock.test
+++ b/tests/clock.test
@@ -37135,7 +37135,29 @@ test clock-46.6 {freescan: regression test - bad time} -constraints valid_off \
 	# 13:00 am/pm are invalid input strings...
 	list [clock scan "13:00 am" -base 0 -gmt 1] \
 	     [clock scan "13:00 pm" -base 0 -gmt 1]
-    } -result {-1 -1}
+    } -result {3600 46800}
+
+if {!$valid_mode} {
+  test clock-46.7a {regression test - switch day by large not-valid time, see bug [3ee8f1c2a785f4d8]} {valid_off} {
+    list [clock scan 23:59:59 -base 0 -gmt 1 -format %H:%M:%S] \
+	 [clock scan 24:00:00 -base 0 -gmt 1 -format %H:%M:%S] \
+	 [clock scan 48:00:00 -base 0 -gmt 1 -format %H:%M:%S]
+  } {86399 86400 172800}
+  test clock-46.7b {freescan: regression test - switch day by large not-valid time, see bug [3ee8f1c2a785f4d8]} {valid_off} {
+    list [clock scan 23:59:59 -base 0 -gmt 1] \
+	 [clock scan 24:00:00 -base 0 -gmt 1] \
+	 [clock scan 48:00:00 -base 0 -gmt 1]
+  } {86399 86400 172800}
+} else {
+  test clock-46.8a {regression test - invalid time (hour)} {
+    list [catch {clock scan 24:00:00 -base 0 -gmt 1 -format %H:%M:%S} msg] $msg \
+	 [catch {clock scan 48:00:00 -base 0 -gmt 1 -format %H:%M:%S} msg] $msg
+  } {1 {unable to convert input string: invalid time (hour)} 1 {unable to convert input string: invalid time (hour)}}
+  test clock-46.8b {freescan: regression test - invalid time (hour)} {
+    list [catch {clock scan 24:00:00 -base 0 -gmt 1} msg] $msg \
+	 [catch {clock scan 48:00:00 -base 0 -gmt 1} msg] $msg
+  } {1 {unable to convert input string: invalid time (hour)} 1 {unable to convert input string: invalid time (hour)}}
+}
 
 proc _invalid_test {args} {
     global valid_mode