Google should now respect X-axis date values for Line, Area, Scatter, and Time Line charts.
For example, if you have the following data*:
| Date | Value |
|------------|-------|
| 01/01/2016 | 3 |
| 02/01/2016 | 4 |
| 03/01/2016 | 5 |
| 03/15/2016 | 6 |
| 09/01/2016 | 3 |
| 12/01/2016 | 3 |
*where the date values are stored as dates. If not, you can use =DateValue()
to convert a date string to a date value.
You'd should see a lot of data in the beginning followed by a lull of activity in the middle of the year.
Area, Line, Scatter, and Time Line (located in Other) should all do so:

By contrast, bar charts continue to treat date values as a simple string and return each of the values sequentially:

And here's a public spreadsheet with all of the included examples