diff --git a/go-mp4/mdhd-box.go b/go-mp4/mdhd-box.go
index e3cc507..8a649ca 100644
--- a/go-mp4/mdhd-box.go
+++ b/go-mp4/mdhd-box.go
@@ -50,11 +50,11 @@ type MediaHeaderBox struct {
 }
 
 func NewMediaHeaderBox() *MediaHeaderBox {
-    _, offset := time.Now().Zone()
+    sec := time.Now().Unix()
     return &MediaHeaderBox{
         Box:               NewFullBox([4]byte{'m', 'd', 'h', 'd'}, 0),
-        Creation_time:     uint64(time.Now().Unix() + int64(offset) + 0x7C25B080),
-        Modification_time: uint64(time.Now().Unix() + int64(offset) + 0x7C25B080),
+        Creation_time:     uint64(sec + 0x7C25B080),
+        Modification_time: uint64(sec + 0x7C25B080),
         Timescale:         1000,
         Language:          [3]byte{'u', 'n', 'd'},
     }
diff --git a/go-mp4/mp4track.go b/go-mp4/mp4track.go
index 911d696..b8dfe55 100644
--- a/go-mp4/mp4track.go
+++ b/go-mp4/mp4track.go
@@ -320,6 +320,7 @@ func (track *mp4track) writeH264(h264 []byte, pts, dts uint64) (err error) {
                     track.height = height
                 }
             }
+            return true // param sets stored in avcC only, not in sample data
         case codec.H264_NAL_PPS:
             ppsid := codec.GetPPSIdWithStartCode(nalu)
             for _, pps := range h264extra.ppss {
@@ -330,6 +331,7 @@ func (track *mp4track) writeH264(h264 []byte, pts, dts uint64) (err error) {
             tmp := make([]byte, len(nalu))
             copy(tmp, nalu)
             h264extra.ppss = append(h264extra.ppss, tmp)
+            return true // param sets stored in avcC only, not in sample data
         }
         //aud/sps/pps/sei 为帧间隔
         //通过first_slice_in_mb来判断，改nalu是否为一帧的开头
@@ -389,10 +391,13 @@ func (track *mp4track) writeH265(h265 []byte, pts, dts uint64) (err error) {
                     track.height = height
                 }
             }
+            return true // param sets stored in hvcC only, not in sample data
         case codec.H265_NAL_PPS:
             h265extra.hvccExtra.UpdatePPS(nalu)
+            return true
         case codec.H265_NAL_VPS:
             h265extra.hvccExtra.UpdateVPS(nalu)
+            return true
         }
 
         if track.lastSample.hasVcl && isH265NewAccessUnit(nalu) {
diff --git a/go-mp4/mvhd-box.go b/go-mp4/mvhd-box.go
index a7afb66..a63799e 100644
--- a/go-mp4/mvhd-box.go
+++ b/go-mp4/mvhd-box.go
@@ -42,11 +42,12 @@ type MovieHeaderBox struct {
 }
 
 func NewMovieHeaderBox() *MovieHeaderBox {
-    _, offset := time.Now().Zone()
+    // ISO 14496-12: creation_time is seconds since 1904-01-01 UTC. Unix() is UTC; do not add Zone offset.
+    sec := time.Now().Unix()
     return &MovieHeaderBox{
         Box:               NewFullBox([4]byte{'m', 'v', 'h', 'd'}, 0),
-        Creation_time:     uint64(time.Now().Unix() + int64(offset) + 0x7C25B080),
-        Modification_time: uint64(time.Now().Unix() + int64(offset) + 0x7C25B080),
+        Creation_time:     uint64(sec + 0x7C25B080),
+        Modification_time: uint64(sec + 0x7C25B080),
         Timescale:         1000,
         Rate:              0x00010000,
         Volume:            0x0100,
diff --git a/go-mp4/tkhd-box.go b/go-mp4/tkhd-box.go
index 96d9197..3c52de3 100644
--- a/go-mp4/tkhd-box.go
+++ b/go-mp4/tkhd-box.go
@@ -48,11 +48,11 @@ type TrackHeaderBox struct {
 }
 
 func NewTrackHeaderBox() *TrackHeaderBox {
-    _, offset := time.Now().Zone()
+    sec := time.Now().Unix()
     return &TrackHeaderBox{
         Box:               NewFullBox([4]byte{'t', 'k', 'h', 'd'}, 0),
-        Creation_time:     uint64(time.Now().Unix() + int64(offset) + 0x7C25B080),
-        Modification_time: uint64(time.Now().Unix() + int64(offset) + 0x7C25B080),
+        Creation_time:     uint64(sec + 0x7C25B080),
+        Modification_time: uint64(sec + 0x7C25B080),
         Layer:             0,
         Alternate_group:   0,
         Matrix:            [9]uint32{0x00010000, 0, 0, 0, 0x00010000, 0, 0, 0, 0x40000000},