X-Git-Url: https://adrianiainlam.tk/git/?a=blobdiff_plain;f=dygraph-tickers.js;h=c6939cbb6eb08e21d89cae5736535974bdc9e40d;hb=4d402efd2ad8318651a7fa809133a47a17db1288;hp=4b4d9dd138c3e1739ceb3c87fc288433ff8693ab;hpb=9a4fd029e0cfd7ed2d89b54659df5e2d6b8b5d9d;p=dygraphs.git

diff --git a/dygraph-tickers.js b/dygraph-tickers.js
index 4b4d9dd..c6939cb 100644
--- a/dygraph-tickers.js
+++ b/dygraph-tickers.js
@@ -392,9 +392,21 @@ Dygraph.getDateAxis = function(start_time, end_time, granularity, opts, dg) {
       // daylight savings transitions. Without this, the ticks could get off
       // by an hour. See tests/daylight-savings.html or issue 147.
       if (check_dst && d.getTimezoneOffset() != start_offset_min) {
-        t += (d.getTimezoneOffset() - start_offset_min) * 60 * 1000;
+        var delta_min = d.getTimezoneOffset() - start_offset_min;
+        t += delta_min * 60 * 1000;
         d = new Date(t);
         start_offset_min = d.getTimezoneOffset();
+
+        // Check whether we've backed into the previous timezone again.
+        // This can happen during a "spring forward" transition. In this case,
+        // it's best to skip this tick altogether (we may be shooting for a
+        // non-existent time like the 2AM that's skipped) and go to the next
+        // one.
+        if (new Date(t + spacing).getTimezoneOffset() != start_offset_min) {
+          t += spacing;
+          d = new Date(t);
+          start_offset_min = d.getTimezoneOffset();
+        }
       }
 
       ticks.push({ v:t,