D3.js ticks every n months, weeks, years, and quarters
Use D3.js ranges to display ticks every n months, weeks, years, and quarters:
```javascript
var xAxis = d3.axisBottom()
xAxis.tickValues(d3.timeMonths(firstQtr, lastQtr, 4))
```
Reference:
https://github.com/d3/d3-time#ranges