Where appropriate, use the modern terms for the one true time base

(UTC) rather than the archaic (GMT) in comments. Except where the
comments are making fun of people doing this (and pedants who insist
on the new terms).

sys/i386/xen/clock.c

@@ -118,7 +118,7 @@ struct mtx clock_lock;
 #define	RTC_UNLOCK	mtx_unlock_spin(&clock_lock)
 #define	NS_PER_TICK	(1000000000ULL/hz)
 
-int adjkerntz;		/* local offset from GMT in seconds */
+int adjkerntz;		/* local offset from UTC in seconds */
 int clkintr_pending;
 int pscnt = 1;
 int psdiv = 1;

sys/kern/subr_fattime.c

@@ -45,7 +45,7 @@
  * Later on again, in Windows NT, timestamps were defined relative to GMT.
  *
  * Purists will point out that UTC replaced GMT for such uses around
- * a century ago, already then.  Ironically "NT" was an abbreviation of 
+ * half a century ago, already then.  Ironically "NT" was an abbreviation of 
  * "New Technology".  Anyway...
  *
  * The 'utc' argument determines if the resulting FATTIME timestamp

sys/netinet/in_systm.h

@@ -44,12 +44,15 @@
  * Internally the system keeps counters in the headers with the bytes
  * swapped so that VAX instructions will work on them.  It reverses
  * the bytes before transmission at each protocol level.  The n_ types
- * represent the types with the bytes in ``high-ender'' order.
+ * represent the types with the bytes in ``high-ender'' order. Network
+ * byte order is usually referered to as big-endian these days rather
+ * than high-ender, which sadly invokes an Orson Scott Card novel, or
+ * worse, the movie.
  */
 typedef u_int16_t n_short;		/* short as received from the net */
 typedef u_int32_t n_long;		/* long as received from the net */
 
-typedef	u_int32_t n_time;		/* ms since 00:00 GMT, byte rev */
+typedef	u_int32_t n_time;		/* ms since 00:00 UTC, byte rev */
 
 #ifdef _KERNEL
 uint32_t	 iptime(void);

sys/netinet/ip_icmp.c

@@ -861,7 +861,7 @@ icmp_send(struct mbuf *m, struct mbuf *opts)
 }
 
 /*
- * Return milliseconds since 00:00 GMT in network format.
+ * Return milliseconds since 00:00 UTC in network format.
  */
 uint32_t
 iptime(void)

sys/netinet/ip_icmp.h

@@ -99,7 +99,7 @@ struct icmp {
 		struct id_ts {			/* ICMP Timestamp */
 			/*
 			 * The next 3 fields are in network format,
-			 * milliseconds since 00:00 GMT
+			 * milliseconds since 00:00 UTC
 			 */
 			uint32_t its_otime;	/* Originate */
 			uint32_t its_rtime;	/* Receive */

sys/sys/sem.h

@@ -37,7 +37,7 @@ struct semid_ds_old {
 	long		sem_pad1;	/* SVABI/386 says I need this here */
 	time_t		sem_ctime;	/* last change time */
     					/* Times measured in secs since */
-    					/* 00:00:00 GMT, Jan. 1, 1970 */
+    					/* 00:00:00 UTC, Jan. 1, 1970, without leap seconds */
 	long		sem_pad2;	/* SVABI/386 says I need this here */
 	long		sem_pad3[4];	/* SVABI/386 says I need this here */
 };
@@ -50,7 +50,7 @@ struct semid_ds {
 	time_t		sem_otime;	/* last operation time */
 	time_t		sem_ctime;	/* last change time */
     					/* Times measured in secs since */
-    					/* 00:00:00 GMT, Jan. 1, 1970 */
+    					/* 00:00:00 UTC, Jan. 1, 1970, without leap seconds */
 };
 
 /*

sys/sys/time.h

@@ -398,7 +398,7 @@ extern sbintime_t sbt_tickthreshold;
  * Functions containing "up" returns time relative to boot and
  * should be used for calculating time intervals.
  *
- * Functions without "up" returns GMT time.
+ * Functions without "up" returns UTC time.
  *
  * Functions with the "get" prefix returns a less precise result
  * much faster than the functions without "get" prefix and should