diff --git a/cache.go b/cache.go
index fb41de3..e61186d 100644
--- a/cache.go
+++ b/cache.go
@@ -199,9 +199,10 @@ func (c *Cache) Map() map[string]CacheObject {
 }
 
 type CacheObject struct {
-	Subject  pkix.Name
-	NotAfter time.Time
-	Paths    []PathObject
+	Subject   pkix.Name
+	NotAfter  time.Time
+	NotBefore time.Time
+	Paths     []PathObject
 }
 
 type PathObject struct {
diff --git a/client.go b/client.go
index 9f39388..b079ed8 100644
--- a/client.go
+++ b/client.go
@@ -104,6 +104,7 @@ type CacheItem struct {
 	Paths      []CacheItemPath `json:"paths"`
 	CommonName string          `json:"common_name"`
 	NotAfter   int64           `json:"not_after"`
+	NotBefore  int64           `json:"not_before"`
 }
 
 type CacheItemPath struct {
diff --git a/core.go b/core.go
index eb06156..3893fa3 100644
--- a/core.go
+++ b/core.go
@@ -89,8 +89,9 @@ func (b *Core) populateUsing(cache *Cache, paths storage.PathList) (*PopulateSta
 					cache.Merge(
 						fmt.Sprintf("%s", sha1.Sum(cert.Raw)),
 						CacheObject{
-							Subject:  cert.Subject,
-							NotAfter: cert.NotAfter,
+							Subject:   cert.Subject,
+							NotAfter:  cert.NotAfter,
+							NotBefore: cert.NotBefore,
 							Paths: []PathObject{
 								{
 									Location: path + ":" + k,
diff --git a/server/manager/source_manager.go b/server/manager/source_manager.go
index 02ff923..37e0f75 100644
--- a/server/manager/source_manager.go
+++ b/server/manager/source_manager.go
@@ -125,6 +125,7 @@ func (s *SourceManager) Data() doomsday.CacheItems {
 			Paths:      paths,
 			CommonName: v.Subject.CommonName,
 			NotAfter:   v.NotAfter.Unix(),
+			NotBefore:  v.NotBefore.Unix(),
 		})
 	}