The datetime widget translates a datetime picker to a datetime string.
datetimedefault: accepts a datetime string, or an empty string to accept blank input; otherwise defaults to current datetimeformat: sets storage format; accepts Moment.js tokens; defaults to raw Date object (if supported by output format)date_format: sets date display format in UI; boolean or Moment.js tokens. If true use default locale format.time_format: sets time display format in UI; boolean or Moment.js tokens. If true use default locale format, false hides time-picker.picker_utc: (default: false) when set to true, the datetime picker will display times in UTC. When false, the datetime picker will display times in the user’s local timezone. When using date-only formats, it can be helpful to set this to true so users in all timezones will see the same date in the datetime picker.