code: func (b *builtinUTCDateSig) evalTime(row chunk.Row) (types.Time, bool, error) {
  	var nowTs = &b.ctx.GetSessionVars().StmtCtx.NowTs
  	if nowTs.Equal(time.Time{}) {
  		*nowTs = time.Now()
  	}
  	year, month, day := nowTs.UTC().Date()
  	result := types.Time{
  		Time: types.FromGoTime(time.Date(year, month, day, 0, 0, 0, 0, time.UTC)),
  		Type: mysql.TypeDate,
  		Fsp:  types.UnspecifiedFsp}
  	return result, false, nil
  }
docs: // evalTime evals UTC_DATE, UTC_DATE().
  // See https://dev.mysql.com/doc/refman/5.7/en/date-and-time-functions.html#function_utc-date