// 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,