1 files changed, 32 insertions, 2 deletions
diff --git a/src/time/zoneinfo_read.go b/src/time/zoneinfo_read.go
index 1e559a62cc..698427b779 100644
--- a/src/time/zoneinfo_read.go
+++ b/src/time/zoneinfo_read.go
@@ -78,6 +78,13 @@ func (d *dataIO) byte() (n byte, ok bool) {
 	return p[0], true
 }
 
+// read returns the read of the data in the buffer.
+func (d *dataIO) rest() []byte {
+	r := d.p
+	d.p = nil
+	return r
+}
+
 // Make a string by stopping at the first NUL
 func byteString(p []byte) string {
 	for i := 0; i < len(p); i++ {
@@ -213,6 +220,12 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
 		return nil, badData
 	}
 
+	var extend string
+	rest := d.rest()
+	if len(rest) > 2 && rest[0] == '\n' && rest[len(rest)-1] == '\n' {
+		extend = string(rest[1 : len(rest)-1])
+	}
+
 	// Now we can build up a useful data structure.
 	// First the zone information.
 	//	utcoff[4] isdst[1] nameindex[1]
@@ -289,7 +302,7 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
 	}
 
 	// Committed to succeed.
-	l := &Location{zone: zone, tx: tx, name: name}
+	l := &Location{zone: zone, tx: tx, name: name, extend: extend}
 
 	// Fill in the cache with information about right now,
 	// since that will be the most common lookup.
@@ -298,10 +311,27 @@ func LoadLocationFromTZData(name string, data []byte) (*Location, error) {
 		if tx[i].when <= sec && (i+1 == len(tx) || sec < tx[i+1].when) {
 			l.cacheStart = tx[i].when
 			l.cacheEnd = omega
+			zoneIdx := tx[i].index
 			if i+1 < len(tx) {
 				l.cacheEnd = tx[i+1].when
+			} else if l.extend != "" {
+				// If we're at the end of the known zone transitions,
+				// try the extend string.
+				if name, _, estart, eend, ok := tzset(l.extend, l.cacheEnd, sec); ok {
+					l.cacheStart = estart
+					l.cacheEnd = eend
+					// Find the zone that is returned by tzset,
+					// the last transition is not always the correct zone.
+					for i, z := range l.zone {
+						if z.name == name {
+							zoneIdx = uint8(i)
+							break
+						}
+					}
+				}
 			}
-			l.cacheZone = &l.zone[tx[i].index]
+			l.cacheZone = &l.zone[zoneIdx]
+			break
 		}
 	}