Update links to other websites

* theory.html: Remove link to Mars Coordinated Time, as it’s a
duplicate.  Omit unnecessary "End_of_mission".
* tz-link.html: Add link to Time Lords (thanks to Arthur David Olson).
Remove links to Tz4Net, efele.net, Whereonearth-timezones, What
Time is it Here?, as these seem to be obsolete or superseded, or
no longer exist.  Say that Shanks is no longer in print.
Update other URLs.

theory.html

@@ -1238,7 +1238,7 @@ <h2 id="planets">Time and time zones on other planets</h2>
 use <a href="https://en.wikipedia.org/wiki/Timekeeping_on_Mars">Mars time</a>.
 Jet Propulsion Laboratory (JPL) coordinators kept Mars time on
 and off during the
-<a href="https://en.wikipedia.org/wiki/Mars_Pathfinder#End_of_mission">Mars
+<a href="https://en.wikipedia.org/wiki/Mars_Pathfinder">Mars
 Pathfinder</a> mission.
 Some of their family members also adapted to Mars time.
 Dozens of special Mars watches were built for JPL workers who kept
@@ -1261,8 +1261,7 @@ <h2 id="planets">Time and time zones on other planets</h2>
 honor of the British astronomer who built the Greenwich telescope that
 defines Earth's prime meridian.
 Mean solar time on the Mars prime meridian is
-called <a href="https://en.wikipedia.org/wiki/Mars_Coordinated_Time">Mars
-Coordinated Time (<abbr>MTC</abbr>)</a>.
+called Mars Coordinated Time (<abbr>MTC</abbr>).
 </p>
 
 <p>

tz-link.html

@@ -189,8 +189,8 @@ <h2 id="changes">Changes to the <code><abbr>tz</abbr></code> database</h2>
 title="International Components for Unicode">ICU</abbr></a>,
 <a href="https://developer.ibm.com/javasdk/support/dst/jtzu/"><abbr>IBM</abbr></a>
 and <a
-href="http://www.oracle.com/technetwork/java/javase/tzupdater-readme-136440.html">Oracle</a>
-Java, <a href="http://www.joda.org/joda-time/tz_update.html">Joda-Time</a>, <a
+href="https://www.oracle.com/technetwork/java/javase/tzupdater-readme-136440.html">Oracle</a>
+Java, <a href="https://www.joda.org/joda-time/tz_update.html">Joda-Time</a>, <a
 href="https://dev.mysql.com/doc/refman/en/time-zone-support.html">MySQL</a>,
 and <a
 href="https://nodatime.org/userguide/tzdb">Noda Time</a> (see below).
@@ -318,11 +318,12 @@ <h2 id="compilers">Other <code><abbr>tz</abbr></code> compilers</h2>
 href="https://www.microsoft.com/net">.NET framework</a>
 and with a <abbr>BSD</abbr>-style license.</li>
 <li><a
-href="http://search.cpan.org/dist/DateTime-TimeZone/">DateTime::TimeZone</a>
+href="https://metacpan.org/release/DateTime-TimeZone">DateTime::TimeZone</a>
 contains a script <code>parse_olson</code> that compiles
 <code><abbr>tz</abbr></code> source into <a href="https://www.perl.org">Perl</a>
 modules. It is part of the Perl <a
-href="http://datetime.perl.org">DateTime Project</a>, which is freely
+href="https://github.com/houseabsolute/DateTime.pm/wiki">DateTime Project</a>,
+which is freely
 available under both the <abbr>GPL</abbr> and the Perl Artistic
 License. DateTime::TimeZone also contains a script
 <code>tests_from_zdump</code> that generates test cases for each clock
@@ -357,15 +358,16 @@ <h2 id="compilers">Other <code><abbr>tz</abbr></code> compilers</h2>
 <li>Java-based compilers and libraries include:
 <ul>
 <li>The <a
-href="http://www.oracle.com/technetwork/java/javase/tzupdater-readme-136440.html">TZUpdater
+href="https://www.oracle.com/technetwork/java/javase/tzupdater-readme-136440.html">TZUpdater
 tool</a> compiles <code><abbr>tz</abbr></code> source into the format used by
 Oracle Java.</li>
 <li>The <a
-href="http://www.oracle.com/technetwork/articles/java/jf14-date-time-2125367.html">Java
-8 <code>java.time</code> <abbr>API</abbr></a> can be supplemented by <a
-href="http://www.threeten.org/threeten-extra/">ThreeTen-Extra</a>,
+href="https://www.oracle.com/technetwork/articles/java/jf14-date-time-2125367.html">Java
+SE <code>java.time</code> <abbr>API</abbr></a> in Java 8 and later
+can be supplemented by <a
+href="https://www.threeten.org/threeten-extra/">ThreeTen-Extra</a>,
 which is freely available under a <abbr>BSD</abbr>-style license.</li>
-<li><a href="http://www.joda.org/joda-time/">Joda-Time &ndash; Java date
+<li><a href="https://www.joda.org/joda-time/">Joda-Time &ndash; Java date
 and time <abbr>API</abbr></a> contains a class
 <code>org.joda.time.tz.ZoneInfoCompiler</code> that compiles
 <code><abbr>tz</abbr></code> source into a binary format. It inspired
@@ -387,11 +389,8 @@ <h2 id="compilers">Other <code><abbr>tz</abbr></code> compilers</h2>
 </ul>
 <li><a href="https://nodatime.org">Noda Time &ndash; Date and
 time <abbr>API</abbr> for .NET</a>
-and <a href="http://www.babiej.demon.nl/Tz4Net/main.htm">TZ4Net</a>
-are similar to Joda-Time and Time4J, but for the .NET framework instead of
-Java. They are freely available under the
-Apache License
-and a <abbr>BSD</abbr>-style license, respectively.</li>
+is like Joda-Time and Time4J, but for the .NET framework instead of Java.
+It is freely available under the Apache License.</li>
 <li><a href="https://en.wikipedia.org/wiki/JavaScript">JavaScript</a>-based
 compilers and libraries include:
 <ul>
@@ -485,7 +484,7 @@ <h2 id="TZif">Other <abbr>TZif</abbr> readers</h2>
 aware. It is freely available under the <abbr>MIT</abbr> license.</li>
 <li>Tcl, mentioned <a href="#Tcl">above</a>, also contains a
 <abbr>TZif</abbr> file reader.</li>
-<li><a href="http://search.cpan.org/perldoc?DateTime::TimeZone::Tzfile">
+<li><a href="https://metacpan.org/pod/DateTime::TimeZone::Tzfile">
 DateTime::TimeZone::Tzfile</a>
 is a <abbr>TZif</abbr> file reader written in Perl.
 It is freely available under the same terms as Perl
@@ -563,8 +562,8 @@ <h2 id="software">Other <code><abbr>tz</abbr></code>-based time zone software</h
 <h2 id="other-dbs">Other time zone databases</h2>
 <ul>
 <li><a href="https://www.astro.com/atlas">Time-zone Atlas</a>
-is Astrodienst's Web version of Shanks and Pottenger's
-time zone history atlases also published in <a
+is Astrodienst's Web version of Shanks and Pottenger's out-of-print
+time zone history atlases now published in <a
 href="https://astrocom.com/astrology-products/software/acs-atlas-software">software</a>
 form by <a href="https://astrocom.com">ACS-Starcrafts</a>.
 These atlases are extensive but unreliable, as Shanks appears to have
@@ -614,8 +613,6 @@ <h2 id="boundaries">Time zone boundaries</h2>
 from several <a href="https://en.wikipedia.org/wiki/Geolocation">geolocation</a>
 services and other sources.</p>
 <ul>
-<li>Databases of time zone boundaries include:
-<ul>
 <li><a href="https://github.com/evansiroky/timezone-boundary-builder">Timezone
 Boundary Builder</a> extracts
 <a href="https://www.openstreetmap.org">Open Street Map</a> data to build
@@ -624,21 +621,6 @@ <h2 id="boundaries">Time zone boundaries</h2>
 its data entries are freely available under the
 <a href="https://opendatacommons.org/licenses/odbl/">Open Data Commons
 Open Database License</a>. The maps' borders appear to be quite accurate.</li>
-<li><a href="http://efele.net/maps/tz/"><abbr>TZ</abbr> timezones
-maps</a> contains <a
-href="https://en.wikipedia.org/wiki/Shapefile">shapefiles</a> of
-sets of <code><abbr>tzdb</abbr></code> timezones. This includes
-<a href="http://efele.net/maps/tz/world/">tz_world</a>, a shapefile
-for all the world's timezones. These maps are no longer maintained and
-are superseded by the Timezone Boundary Builder.</li>
-<li><a
-href="https://github.com/straup/whereonearth-timezone">Whereonearth-timezone</a>
-is in <a href="https://tools.ietf.org/html/rfc7946">GeoJSON</a> format
-(Internet <abbr>RFC</abbr> 7946), and combines the
-the tz_world shapefiles with the
-<a href="https://developer.yahoo.com/geo/geoplanet/">GeoPlanet</a>
-dataset.</li>
-</ul></li>
 <li>Programmatic interfaces that map geographical coordinates via tz_world to
 <code><abbr>tzdb</abbr></code> timezones include:
 <ul>
@@ -663,13 +645,13 @@ <h2 id="boundaries">Time zone boundaries</h2>
 <li>The <a
 href="https://github.com/gunyarakun/timezone_finder">timezone_finder</a>
 library for Ruby is freely available under the MIT license.</li>
-<li><a href="https://derickrethans.nl/what-time-is-it.html">What Time
-is It Here?</a> applies MongoDB
-geospatial query operators to shapefiles' data.</li>
 </ul></li>
 <li>Free access via a network API, if you register a key, is provided by
-the <a href="http://www.geonames.org/export/web-services.html#timezone">GeoNames Timezone web service</a>,
-the <a href="https://developers.google.com/maps/documentation/timezone/intro">Google Maps Time Zone API</a>, and
+the <a
+href="https://www.geonames.org/export/web-services.html#timezone">GeoNames
+Timezone web service</a>, the <a
+href="https://developers.google.com/maps/documentation/timezone/intro">Google
+Maps Time Zone API</a>, and
 the <a href="https://timezonedb.com">Time Zone Database &amp; API</a>.
 Commercial network API access is provided
 by <a href="https://askgeo.com">AskGeo</a>
@@ -705,15 +687,16 @@ <h2 id="civil">Civil time concepts and history</h2>
 <li><a href="https://www.nist.gov/pml/time-and-frequency-division/popular-links/walk-through-time">A
 Walk through Time</a>
 surveys the evolution of timekeeping.</li>
-<li><a href="http://www.webexhibits.org/daylightsaving/">About Daylight
-Saving Time &ndash; History, rationale, laws &amp; dates</a>
-is an overall history of <abbr>DST</abbr>.</li>
+<li>The history of daylight saving time is surveyed in <a
+href="http://www.webexhibits.org/daylightsaving/">About Daylight
+Saving Time &ndash; History, rationale, laws &amp; dates</a> and summarized in
+<a href="http://seizethedaylight.com/dst/">A Brief
+History of Daylight Saving Time</a>.</li>
+<li><a href="https://www.laphamsquarterly.org/roundtable/time-lords">Time
+Lords</a> discusses how authoritarians manipulate civil time.</li>
 <li><a href="https://www.w3.org/TR/timezone/">Working with Time Zones</a>
 contains guidelines and best practices for software applications that
 deal with civil time.</li>
-<li><a href="http://seizethedaylight.com/dst/">A Brief
-History of Daylight Saving Time</a> summarizes some of the contentious
-history of <abbr>DST</abbr>.</li>
 <li><a href="https://www.staff.science.uu.nl/~gent0113/idl/idl.htm">A History of
 the International Date Line</a> tells the story of the most important
 time zone boundary.</li>
@@ -731,7 +714,7 @@ <h2 id="national">National histories of legal time</h2>
 Dates of Daylight Savings Time within Australia</a>.</dd>
 <dt>Belgium</dt>
 <dd>The Royal Observatory of Belgium maintains a table of <a
-href="http://www.astro.oma.be/GENERAL/INFO/nli001a.html"
+href="https://www.astro.oma.be/GENERAL/INFO/nli001a.html"
 hreflang="nl">time in Belgium (in Dutch)</a>.</dd>
 <dt>Brazil</dt>
 <dd>The Time Service Department of the National Observatory
@@ -745,7 +728,7 @@ <h2 id="national">National histories of legal time</h2>
 zones &amp; daylight saving time</a>.</dd>
 <dt>Chile</dt>
 <dd>The Hydrographic and Oceanographic Service of the Chilean Navy publishes a
-<a href="http://www.horaoficial.cl/historia_hora.html" hreflang="es">history of
+<a href="https://www.horaoficial.cl/historia_hora.html" hreflang="es">history of
 Chile's official time (in Spanish)</a>.</dd>
 <dt>China</dt>
 <dd>The Hong Kong Observatory maintains a
@@ -769,8 +752,8 @@ <h2 id="national">National histories of legal time</h2>
 hreflang="he">announcements (in Hebrew)</a>.</dd>
 <dt>Italy</dt>
 <dd>The National Institute of Metrological Research maintains a
-<a href="http://oldsite.inrim.it/res/tf/ora_legale_i.shtml">table of civil time
-(in Italian)</a>.</dd>
+<a href="http://oldsite.inrim.it/res/tf/ora_legale_i.shtml" hreflang="it">table
+of civil time (in Italian)</a>.</dd>
 <dt>Malaysia</dt>
 <dd>See Singapore <a href="#Singapore">below</a>.</dd>
 <dt>Mexico</dt>