Disable parts of the timeline as the dates for them pass

As each date in the timeline passes, it will show as "disabled" to show that that item has passed. I've styled it as such:

![](https://cloud.githubusercontent.com/assets/494732/3321681/d692bfa6-f73a-11e3-8385-6b9bf4a47e23.png)

Well for this class, no, as that would mean that it is a `UtcDateTimeOffsetProvider`. :wink: 

Getting `DateTimeOffset.Now` gives a local time, but with the correct offset, meaning that TimeZone issues don't come into play, but making it easier to work with as you are always in the correct time/time zone.