From 59d72d6bb3ab23a866f566906a87ac00e44613dd Mon Sep 17 00:00:00 2001
From: alexcjohnson <alex@plot.ly>
Date: Thu, 26 Jul 2018 16:36:10 +0100
Subject: [PATCH] fix #1363 - honor tenths of milliseconds in old numeric date
 data

---
 src/plots/cartesian/set_convert.js |  9 ++++++++-
 test/jasmine/tests/axes_test.js    | 12 ++++++++++--
 2 files changed, 18 insertions(+), 3 deletions(-)

diff --git a/src/plots/cartesian/set_convert.js b/src/plots/cartesian/set_convert.js
index d3471547328..6accda70654 100644
--- a/src/plots/cartesian/set_convert.js
+++ b/src/plots/cartesian/set_convert.js
@@ -92,7 +92,14 @@ module.exports = function setConvert(ax, fullLayout) {
         // as (local) ms if that fails.
         var ms = dateTime2ms(v, calendar || ax.calendar);
         if(ms === BADNUM) {
-            if(isNumeric(v)) ms = dateTime2ms(new Date(+v));
+            if(isNumeric(v)) {
+                v = +v;
+                // keep track of tenths of ms, that `new Date` will drop
+                // same logic as in Lib.ms2DateTime
+                var msecTenths = Math.floor(Lib.mod(v + 0.05, 1) * 10);
+                var msRounded = Math.round(v - msecTenths / 10);
+                ms = dateTime2ms(new Date(msRounded)) + msecTenths / 10;
+            }
             else return BADNUM;
         }
         return ms;
diff --git a/test/jasmine/tests/axes_test.js b/test/jasmine/tests/axes_test.js
index 7b6352a605e..fa5fd0b2dd4 100644
--- a/test/jasmine/tests/axes_test.js
+++ b/test/jasmine/tests/axes_test.js
@@ -2510,10 +2510,18 @@ describe('Test axes', function() {
             });
 
             it('- date case', function() {
+                var msLocal = new Date(2000, 0, 1).getTime();
+                var msUTC = 946684800000;
                 var out = _makeCalcdata({
-                    x: ['2000-01-01', NaN, null, new Date(2000, 0, 1).getTime()],
+                    x: ['2000-01-01', NaN, null, msLocal],
                 }, 'x', 'date');
-                expect(out).toEqual([946684800000, BADNUM, BADNUM, 946684800000]);
+                expect(out).toEqual([msUTC, BADNUM, BADNUM, msUTC]);
+
+                // fractional milliseconds - should round to 0.1 msec
+                var out2 = _makeCalcdata({
+                    x: [msLocal, msLocal + 0.04, msLocal + 0.06, msLocal + 0.5, msLocal + 0.94, msLocal + 0.96, msLocal + 1]
+                }, 'x', 'date');
+                expect(out2).toEqual([msUTC, msUTC, msUTC + 0.1, msUTC + 0.5, msUTC + 0.9, msUTC + 1, msUTC + 1]);
             });
 
             it('- category case', function() {