Some small changes so that visually everything falls in to place by default.

form-item--date.scss

@@ -45,7 +45,9 @@
   border: 1px solid #4D4D4D;
   box-shadow: 1px 1px 2px 0 rgba(0,0,0,0.34);
   border-radius: 19px;
-  padding: 26px 20px;
+  padding: 0.4rem 2rem;
+  z-index: 2!important;
+  width: auto !important;
 }
 
 // Hide the left and right arrows.
@@ -72,9 +74,9 @@
     height: 30px;
     display: inline-block;
     border-radius: 5px;
-    font-size: 21px;
+    font-size: 16px;
     transition: all 0.2s ease;
-    line-height: 30px;
+    text-align: center !important;
     &:hover,
     &:focus {
       color: #4D4D4D;