When calculating the ticks, should use the date that is closest

to the tick date, even if that date is smaller than the tick date.
Currently it only uses the closest date that is greater than
the tick date.

src/scale/financetime.js

@@ -308,7 +308,16 @@ module.exports = function(d3_scale_linear, d3_time, d3_bisect, techan_util_rebin
     return function(d) {
       var value = visibleDomainLookup[+d];
       if (value !== undefined) return visibleDomain[value];
-      return visibleDomain[d3_bisect(visibleDomain, d)];
+      var index = d3_bisect(visibleDomain, d);
+      if (index > 0) {
+        // d3_bisect gets the index of the closest value that is the greater than d,
+        // which may not be the value that is closest to d.
+        // If the closest value that is smaller than d is closer, choose that instead.
+        if ((+d - (+visibleDomain[index-1])) < (+visibleDomain[index] - +d)) {
+          index--;
+        }
+      }
+      return visibleDomain[index];
     };
   }
 

test/spec/bundle/scale/financetimeSpec.js

@@ -190,6 +190,7 @@ techanModule('scale/financetime', function(specBuilder) {
 
         it('Then ticks with specified interval and step count returns that number', function() {
           expect(financetime.ticks(d3.time.day, 2)).toEqual([
+            new Date(2012,4,18),
             new Date(2012,4,21),
             new Date(2012,4,23),
             new Date(2012,4,25),
@@ -425,6 +426,7 @@ techanModule('scale/financetime', function(specBuilder) {
 
             it('Then ticks with specified interval and step count returns that number', function() {
               expect(financetime.ticks(d3.time.day, 2)).toEqual([
+                new Date(2012,4,18),
                 new Date(2012,4,21),
                 new Date(2012,4,23),
                 new Date(2012,4,25),
@@ -627,4 +629,4 @@ techanModule('scale/financetime', function(specBuilder) {
       });
     });
   });
-});
+});