Time Unit

{
  "data": ... ,
  "mark": ... ,
  "encoding": {
    "x": {
      "timeUnit": ...,               // time unit
      "field": ...,
      "type": "temporal",
      ...
    },
    "y": ...,
    ...
  },
  ...
}

timeUnit property of a channel definition sets the level of specificity for a temporal field. Currently supported values are:

Non-periodic Time Unit: 'year', 'yearmonth', 'yearmonthday', 'yearmonthdate', 'yearday', 'yeardate', 'yearmonthdayhours', 'yearmonthdayhoursminutes'.
- For example the yearmonth of April 4, 2016 11:52:34 is April 2016.
Periodic Time Unit: 'month', 'day', 'date', 'hours', 'minutes', 'seconds', 'milliseconds', 'hoursminutes', 'hoursminutesseconds', 'minutesseconds', 'secondsmilliseconds'.

Date/Time Units

Vega-Lite supports the following time units, which can be combined into the timeUnit properties above (e.g. yearmonthday, hoursminutes).

Function	Description	Example value for `Monday April 4, 2016 11:52:34:0201`
`date`	returns the day of the month for a given date input, in local time.	`4`
`day`	returns the day of the week for a given date input, in local time. (`0` for Sunday, `1` for Monday, `2` for Tuesday, and so on.)	`1`
`year`	returns the year for a given date input, in local time.	`2016`
`month`	returns the (zero-based) month for a given date input, in local time (e.g., `0` for January).	`3`
`hours`	returns the hours component for a given date input, in local time (number between `0` and `23`).	`11`
`minutes`	returns the minutes component for a given date input, in local time (number between `0` and `59`).	`52`
`seconds`	returns the seconds component for a given date input, in local time (number between `0` and `59`).	`34`
`milliseconds`	returns the milliseconds component for a given date input, in local time (number between `0` and `999`).	`201`

Example

This example shows temperature in Seattle over the months.