Consistently refer to UTC/Greenwich for offsets

This helps aid understanding of the concept

src-standard/main/java/javax/time/chrono/ChronoOffsetDateTime.java

@@ -47,16 +47,16 @@
 import javax.time.zone.ZoneResolvers;
 
 /**
- * A date-time with a zone offset from UTC for the calendar neutral API.
+ * A date-time with a zone offset from UTC/Greenwich for the calendar neutral API.
  * <p>
  * {@code ChronoOffsetDateTime} is an immutable representation of a date-time with an offset.
  * This class stores all date and time fields, to a precision of nanoseconds,
- * as well as the offset from UTC. For example, the value
+ * as well as the offset from UTC/Greenwich. For example, the value
  * "2nd October 2007 at 13:45.30.123456789 +02:00" can be stored in an {@code OffsetDateTime}.
  * <p>
  * {@code ChronoOffsetDateTime} and {@link Instant} both store an instant on the time-line
  * to nanosecond precision. The main difference is that this class also stores the
- * offset from UTC. {@code Instant} should be used when you only need to compare the
+ * offset from UTC/Greenwich. {@code Instant} should be used when you only need to compare the
  * object to other instants. {@code ChronoOffsetDateTime} should be used when you want to actively
  * query and manipulate the date and time fields, although you should also consider using
  * {@link ChronoZonedDateTime}.

src-standard/main/java/javax/time/chrono/ChronoOffsetDateTimeImpl.java

@@ -66,16 +66,16 @@
 import javax.time.zone.ZoneRules;
 
 /**
- * A date-time with a zone offset from UTC for the calendar neutral API.
+ * A date-time with a zone offset from UTC/Greenwich for the calendar neutral API.
  * <p>
  * {@code ChronoOffsetDateTime} is an immutable representation of a date-time with an offset.
  * This class stores all date and time fields, to a precision of nanoseconds,
- * as well as the offset from UTC. For example, the value
+ * as well as the offset from UTC/Greenwich. For example, the value
  * "2nd October 2007 at 13:45.30.123456789 +02:00" can be stored in an {@code OffsetDateTime}.
  * <p>
  * {@code ChronoOffsetDateTime} and {@link Instant} both store an instant on the time-line
  * to nanosecond precision. The main difference is that this class also stores the
- * offset from UTC. {@code Instant} should be used when you only need to compare the
+ * offset from UTC/Greenwich. {@code Instant} should be used when you only need to compare the
  * object to other instants. {@code ChronoOffsetDateTime} should be used when you want to actively
  * query and manipulate the date and time fields, although you should also consider using
  * {@link ChronoZonedDateTime}.

src/main/java/javax/time/OffsetDate.java

@@ -55,7 +55,7 @@
 import javax.time.zone.ZoneResolvers;
 
 /**
- * A date with a zone offset from UTC in the ISO-8601 calendar system,
+ * A date with a zone offset from UTC/Greenwich in the ISO-8601 calendar system,
  * such as {@code 2007-12-03+01:00}.
  * <p>
  * {@code OffsetDate} is an immutable date-time object that represents a date, often viewed
@@ -79,11 +79,11 @@ public final class OffsetDate
     private static final long serialVersionUID = -3618963189L;
 
     /**
-     * The date.
+     * The date, not null.
      */
     private final LocalDate date;
     /**
-     * The zone offset.
+     * The zone offset, not null.
      */
     private final ZoneOffset offset;
 

src/main/java/javax/time/OffsetDateTime.java

@@ -60,17 +60,17 @@
 import javax.time.zone.ZoneRules;
 
 /**
- * A date-time with a zone offset from UTC in the ISO-8601 calendar system,
+ * A date-time with a zone offset from UTC/Greenwich in the ISO-8601 calendar system,
  * such as {@code 2007-12-03T10:15:30+01:00}.
  * <p>
  * {@code OffsetDateTime} is an immutable representation of a date-time with an offset.
  * This class stores all date and time fields, to a precision of nanoseconds,
- * as well as the offset from UTC. For example, the value
+ * as well as the offset from UTC/Greenwich. For example, the value
  * "2nd October 2007 at 13:45.30.123456789 +02:00" can be stored in an {@code OffsetDateTime}.
  * <p>
  * {@code OffsetDateTime} and {@link Instant} both store an instant on the time-line
  * to nanosecond precision. The main difference is that this class also stores the
- * offset from UTC. {@code Instant} should be used when you only need to compare the
+ * offset from UTC/Greenwich. {@code Instant} should be used when you only need to compare the
  * object to other instants. {@code OffsetDateTime} should be used when you want to actively
  * query and manipulate the date and time fields, although you should also consider using
  * {@link ZonedDateTime}.
@@ -89,11 +89,11 @@ public final class OffsetDateTime
     private static final long serialVersionUID = -456761901L;
 
     /**
-     * The local date-time.
+     * The local date-time, not null.
      */
     private final LocalDateTime dateTime;
     /**
-     * The zone offset.
+     * The zone offset, not null.
      */
     private final ZoneOffset offset;
 

src/main/java/javax/time/OffsetTime.java

@@ -55,7 +55,7 @@
 import javax.time.jdk8.DefaultInterfaceDateTimeAccessor;
 
 /**
- * A time with a zone offset from UTC in the ISO-8601 calendar system,
+ * A time with a zone offset from UTC/Greenwich in the ISO-8601 calendar system,
  * such as {@code 10:15:30+01:00}.
  * <p>
  * {@code OffsetTime} is an immutable date-time object that represents a time, often
@@ -82,7 +82,7 @@ public final class OffsetTime
      */
     private final LocalTime time;
     /**
-     * The zone offset from UTC, not null.
+     * The zone offset, not null.
      */
     private final ZoneOffset offset;
 

src/main/java/javax/time/zone/ZoneResolvers.java

@@ -43,7 +43,7 @@
  * Provides common implementations of {@code ZoneResolver}.
  * <p>
  * A {@link ZoneResolver} provides a strategy for handling the gaps and overlaps
- * on the time-line that occur due to changes in the offset from UTC, usually
+ * on the time-line that occur due to changes in the offset from UTC/Greenwich, usually
  * caused by daylight saving time.
  * 
  * <h4>Implementation notes</h4>

src/main/java/javax/time/zone/ZoneRulesBuilder.java

@@ -86,8 +86,8 @@ class ZoneRulesBuilder {
      * Constructs an instance of the builder that can be used to create zone rules.
      * <p>
      * The builder is used by adding one or more windows representing portions
-     * of the time-line. The standard offset from UTC will be constant within a window,
-     * although two adjacent windows can have the same standard offset.
+     * of the time-line. The standard offset from UTC/Greenwich will be constant
+     * within a window, although two adjacent windows can have the same standard offset.
      * <p>
      * Within each window, there can either be a
      * {@link #setFixedSavingsToWindow fixed savings amount} or a