1）假设您可以在输入字段中输入日期，而日历仅是图标。你可以有这样的帮助方法

    public String threeDaysBefore(){
    String threeDaysBefore = "";
    Date date = new Date();
    Calendar cal = Calendar.getInstance();
    cal.setTime(date);

    cal.add(Calendar.DAY_OF_YEAR, -3);
    Date before = cal.getTime();
    SimpleDateFormat formatter = new SimpleDateFormat("dd.MM.yyyy HH:mm");
    threeDaysBefore = formatter.format(before);
    return threeDaysBefore;
}

然后在代码中

  WebElement calendarManualInput = driver.findElement...// find the manual input field
  calendarManualInput.sendKeys(threeDaysBefore());

2）如果您只能单击日历，那将更加棘手。您仍然需要String，但有一点不同：

    public String threeDaysBefore(){
    String threeDaysBefore = "";
    Date date = new Date();
    Calendar cal = Calendar.getInstance();
    cal.setTime(date);

    cal.add(Calendar.DAY_OF_YEAR, -3);
    Date before = cal.getTime();
    SimpleDateFormat formatter = new SimpleDateFormat("dd");
    threeDaysBefore = formatter.format(before);
    return threeDaysBefore;
}

但是，上面没有什么收获。如果日期是1.4。那么它将返回“ 29”，可以解释为29.4。你不想发生。因此，在代码后面，您可能必须这样做

//this will click three days before
Date today = new Date();
Date minusThree = new Date();
Calendar now = Calendar.getInstance();
now.setTime(today);
Calendar before = Calendar.getInstance();
before.setTime(minusThree);
before.add(Calendar.DAY_OF_YEAR, -3);
int monthNow = now.get(Calendar.MONTH);
int monthBefore = before.get(Calendar.MONTH);

if (monthBefore < monthNow){
  // click previous month in the calendar tooltip on page
}
WebElement dateToSelect = driver.findElement(By.xpath("//span[text()='"+threeDaysBefore()+"']"));
dateToSelect.click();