| `round` | `String` | `false` | If defined, dates will be rounded to the start of this unit. See [Time Units](#scales-time-units) below for the allowed units.
| `tooltipFormat` | `String` | | The moment js format string to use for the tooltip.
| `unit` | `String` | `false` | If defined, will force the unit to be a certain type. See [Time Units](#scales-time-units) section below for details.
-| `unitStepSize` | `Number` | `1` | The number of units between grid lines.
+| `stepSize` | `Number` | `1` | The number of units between grid lines.
| `minUnit` | `String` | `millisecond` | The minimum display format to be used for a time unit.
## Date Formats