diff --git a/mod/forum/classes/output/big_search_form.php b/mod/forum/classes/output/big_search_form.php
index b4ae556b065..919e46a1800 100644
--- a/mod/forum/classes/output/big_search_form.php
+++ b/mod/forum/classes/output/big_search_form.php
@@ -214,17 +214,19 @@ class big_search_form implements renderable, templatable {
             $dateto = time() + HOURSECS;
         }
 
-        $data->datefromfields = html_writer::select_time('days', 'fromday', $datefrom)
-                              . html_writer::select_time('months', 'frommonth', $datefrom)
-                              . html_writer::select_time('years', 'fromyear', $datefrom)
-                              . html_writer::select_time('hours', 'fromhour', $datefrom)
-                              . html_writer::select_time('minutes', 'fromminute', $datefrom);
+        $data->datefromfields = html_writer::div(html_writer::select_time('days', 'fromday', $datefrom), 'form-group fitem ml-2')
+                              . html_writer::div(html_writer::select_time('months', 'frommonth', $datefrom),
+                           'form-group fitem ml-2')
+                              . html_writer::div(html_writer::select_time('years', 'fromyear', $datefrom), 'form-group fitem ml-2')
+                              . html_writer::div(html_writer::select_time('hours', 'fromhour', $datefrom), 'form-group fitem ml-2')
+                              . html_writer::div(html_writer::select_time('minutes', 'fromminute', $datefrom),
+                           'form-group fitem ml-2');
 
-        $data->datetofields = html_writer::select_time('days', 'today', $dateto)
-                            . html_writer::select_time('months', 'tomonth', $dateto)
-                            . html_writer::select_time('years', 'toyear', $dateto)
-                            . html_writer::select_time('hours', 'tohour', $dateto)
-                            . html_writer::select_time('minutes', 'tominute', $dateto);
+        $data->datetofields = html_writer::div(html_writer::select_time('days', 'today', $dateto), 'form-group fitem ml-2')
+                            . html_writer::div(html_writer::select_time('months', 'tomonth', $dateto), 'form-group fitem ml-2')
+                            . html_writer::div(html_writer::select_time('years', 'toyear', $dateto), 'form-group fitem ml-2')
+                            . html_writer::div(html_writer::select_time('hours', 'tohour', $dateto), 'form-group fitem ml-2')
+                            . html_writer::div(html_writer::select_time('minutes', 'tominute', $dateto), 'form-group fitem ml-2');
 
         if ($this->forumid && !empty($this->forumoptions)) {
             foreach ($this->forumoptions as $index => $option) {
diff --git a/mod/forum/templates/big_search_form.mustache b/mod/forum/templates/big_search_form.mustache
index 4d26e5c24cb..2f10c16e3f2 100644
--- a/mod/forum/templates/big_search_form.mustache
+++ b/mod/forum/templates/big_search_form.mustache
@@ -93,8 +93,10 @@
                     {{#str}}searchdatefrom, forum{{/str}}
                 </td>
                 <td class="c1">
+                    <div class="fdate_time_selector d-flex flex-wrap align-items-center">
                     <input type="checkbox" name="timefromrestrict" value="1" {{#datefromchecked}}checked{{/datefromchecked}}>
-                    {{{datefromfields}}}
+                        {{{datefromfields}}}
+                    </div>
                     <input type="hidden" name="hfromday" value="0">
                     <input type="hidden" name="hfrommonth" value="0">
                     <input type="hidden" name="hfromyear" value="0">
@@ -107,8 +109,10 @@
                     {{#str}}searchdateto, forum{{/str}}
                 </td>
                 <td class="c1">
+                    <div class="fdate_time_selector d-flex flex-wrap align-items-center">
                     <input type="checkbox" name="timetorestrict" value="1" {{#datetochecked}}checked{{/datetochecked}}>
-                    {{{datetofields}}}
+                        {{{datetofields}}}
+                    </div>
                     <input type="hidden" name="htoday" value="0">
                     <input type="hidden" name="htomonth" value="0">
                     <input type="hidden" name="htoyear" value="0">
diff --git a/theme/boost/templates/core/select_time.mustache b/theme/boost/templates/core/select_time.mustache
index f2c9029613e..df48117bd2c 100644
--- a/theme/boost/templates/core/select_time.mustache
+++ b/theme/boost/templates/core/select_time.mustache
@@ -31,7 +31,7 @@
     }
 }}
 <label for="{{id}}" class="sr-only">{{label}}</label>
-<select name="{{name}}" id="{{id}}"{{#attributes}} {{name}}="{{value}}"{{/attributes}} class="form-control">
+<select name="{{name}}" id="{{id}}"{{#attributes}} {{name}}="{{value}}"{{/attributes}} class="form-control custom-select">
     {{#options}}
         <option value="{{value}}" {{#selected}}selected{{/selected}}>{{name}}</option>
     {{/options}}
diff --git a/theme/boost/templates/mod_forum/big_search_form.mustache b/theme/boost/templates/mod_forum/big_search_form.mustache
index 5c05e5c7edc..dc5c6066b1c 100644
--- a/theme/boost/templates/mod_forum/big_search_form.mustache
+++ b/theme/boost/templates/mod_forum/big_search_form.mustache
@@ -51,10 +51,10 @@
     {{#str}}searchforumintro, forum{{/str}}
 </div>
 <div class="box generalbox boxaligncenter">
-    <form id="searchform" action="{{actionurl}}" method="get">
+    <form id="searchform" class="mform" action="{{actionurl}}" method="get">
         <table class="searchbox table table-striped" id="form">
             <tr>
-                <td class="c0 text-xs-right">
+                <td class="c0 text-xs-right align-bottom">
                     <label for="words">{{#str}}searchwords, forum{{/str}}</label>
                     <input type="hidden" value="{{courseid}}" name="id">
                 </td>
@@ -63,7 +63,7 @@
                 </td>
             </tr>
             <tr>
-                <td class="c0 text-xs-right">
+                <td class="c0 text-xs-right align-bottom">
                     <label for="phrase">{{#str}}searchphrase, forum{{/str}}</label>
                 </td>
                 <td class="c1">
@@ -71,7 +71,7 @@
                 </td>
             </tr>
             <tr>
-                <td class="c0 text-xs-right">
+                <td class="c0 text-xs-right align-bottom">
                     <label for="notwords">{{#str}}searchnotwords, forum{{/str}}</label>
                 </td>
                 <td class="c1">
@@ -80,7 +80,7 @@
             </tr>
             {{#showfullwords}}
                 <tr>
-                    <td class="c0 text-xs-right">
+                    <td class="c0 text-xs-right align-bottom">
                         <label for="fullwords">{{#str}}searchfullwords, forum{{/str}}</label>
                     </td>
                     <td class="c1">
@@ -89,12 +89,14 @@
                 </tr>
             {{/showfullwords}}
             <tr>
-                <td class="c0 text-xs-right">
-                    {{#str}}searchdatefrom, forum{{/str}}
+                <td class="c0 text-xs-right align-bottom">
+                    <label for="timetorestrict">{{#str}}searchdatefrom, forum{{/str}}</label>
                 </td>
                 <td class="c1 text-nowrap form-inline">
-                    <input type="checkbox" name="timefromrestrict" value="1" {{#datefromchecked}}checked{{/datefromchecked}}>
-                    {{{datefromfields}}}
+                    <div class="fdate_time_selector d-flex flex-wrap align-items-center">
+                        <input type="checkbox" name="timefromrestrict" value="1" {{#datefromchecked}}checked{{/datefromchecked}}>
+                        {{{datefromfields}}}
+                    </div>
                     <input type="hidden" name="hfromday" value="0">
                     <input type="hidden" name="hfrommonth" value="0">
                     <input type="hidden" name="hfromyear" value="0">
@@ -103,12 +105,14 @@
                 </td>
             </tr>
             <tr>
-                <td class="c0 text-xs-right">
-                    {{#str}}searchdateto, forum{{/str}}
+                <td class="c0 text-xs-right align-bottom">
+                    <label for="timetorestrict">{{#str}}searchdateto, forum{{/str}}</label>
                 </td>
                 <td class="c1 text-nowrap form-inline">
-                    <input type="checkbox" name="timetorestrict" value="1" {{#datetochecked}}checked{{/datetochecked}}>
-                    {{{datetofields}}}
+                    <div class="fdate_time_selector d-flex flex-wrap align-items-center">
+                        <input type="checkbox" name="timetorestrict" value="1" {{#datetochecked}}checked{{/datetochecked}}>
+                        {{{datetofields}}}
+                    </div>
                     <input type="hidden" name="htoday" value="0">
                     <input type="hidden" name="htomonth" value="0">
                     <input type="hidden" name="htoyear" value="0">
@@ -117,11 +121,11 @@
                 </td>
             </tr>
             <tr>
-                <td class="c0 text-xs-right">
+                <td class="c0 text-xs-right align-bottom">
                     <label for="menuforumid">{{#str}}searchwhichforums, forum{{/str}}</label>
                 </td>
                 <td class="c1">
-                    <select name="forumid" id="menuforumid" class="form-control">
+                    <select name="forumid" id="menuforumid" class="form-control custom-select">
                         {{#forumoptions}}
                             <option value="{{value}}" {{#selected}}selected{{/selected}}>{{name}}</option>
                         {{/forumoptions}}
@@ -129,7 +133,7 @@
                 </td>
             </tr>
             <tr>
-                <td class="c0 text-xs-right">
+                <td class="c0 text-xs-right align-bottom">
                     <label for="subject">{{#str}}searchsubject, forum{{/str}}</label>
                 </td>
                 <td class="c1">
@@ -137,7 +141,7 @@
                 </td>
             </tr>
             <tr>
-                <td class="c0 text-xs-right">
+                <td class="c0 text-xs-right align-bottom">
                     <label for="user">{{#str}}searchuser, forum{{/str}}</label>
                 </td>
                 <td class="c1">
@@ -147,7 +151,7 @@
             {{#tagsenabled}}
                 <tr>
                     <td class="c0">
-                        <label for="tags">{{#str}}searchtags, forum{{/str}}</label>
+                        <label for="tags" class="mt-1">{{#str}}searchtags, forum{{/str}}</label>
                     </td>
                     <td class="c1">
                         <select class="custom-select" name="tags[]"