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Date validation

Hi all

I'm using the calendar question from the library, allowing folk to either enter the date directly or enter from the calendar.  I want to verify that what they enter is a valid date (ie not after today).  

When I enter a date that's not valid, it lets me through, but just saves it as if I entered today's date.  What I'd like is an error message to come up.  Can someone help please?  Here's what I have:

var now = Date.now();

if (!$('#[% QuestionName() %]_Unix').val()) {
    strErrorMessage = 'A response is required.';

if (SSI_GetValue('Calendar_Unix') > now){
    strErrorMessage = "You can't enter a date that is in the future.";
asked Jan 18 by Marion Silver (5,240 points)
AHA!  I should be using UserInput rather than Unix.  If I enter any numbers AT ALL, even if it isn't a date, it's allowed through.  So first of all, I need to make sure the ONLY dates are allowed to be entered.  Then I can validate against today's date.
Yeah, respondents being able to freely type into the input opens a big can of worms once you consider the possibility of bad input.  I gave the input element the "readonly" attribute by default to avoid this altogether.

There wasn't an easy way for me to write custom verification to test that user-written input is valid because the question supports any arbitrary date format, but it shouldn't be too hard to write some specific validation code if I know exactly what date format you are using.
Cheers, Zachary!  I'd be after dd/mm/yyyy date format.

1 Answer

0 votes
Best answer
Please try out this verification:

// Settings
var invalidFormat = 'Response was not recognized as a date.';
var invalidDate = 'Response was not a real date.';
var futureDate = 'Response cannot be a future date.';

// Run
var resp = $('#[% QuestionName() %]_UserInput').val();
var match = resp.match(/^\s*(\d{1,2})\/(\d{1,2})\/(\d{1,4})\s*$/);

if (!match) {
    strErrorMessage = invalidFormat;

else {
    var day = Number(match[1]);
    var month = Number(match[2]);
    var year = Number(match[3]);
    var maxDay = 31;
    switch (month) {
        case 4:
        case 6:
        case 9:
        case 11:
            maxDay = 30;
        case 2:
            maxDay = 28;
            if (year % 4 == 0 && (year % 100 != 0 || year % 400 == 0)) {
                maxDay = 29;
    if (day < 1 || day > maxDay || month < 1 || month > 12) {
        strErrorMessage = invalidDate;
    else if (new Date(year, month - 1, day) > new Date()) {
        strErrorMessage = futureDate;
answered Jan 18 by Zachary Platinum Sawtooth Software, Inc. (205,975 points)
selected Jan 19 by Paul Moon
Wow!  That's great, Zachary!  Now I'm guessing I take the UserInput, turn it into Unix, and then compare to today's date.  I'll give that a crack.
So 31/01/2022 triggers the futureDate error.  31/1/2022 does too.  But 31/1/22 goes through.
So we need to support two-digit years?  One catch with that is interpreting whether that represents the current century or the last - "40" could be the past date 1940 or the future date 2040.  Is there a minimum date you are allowing for your calendar question that we could use as a cutoff to make this determination?
Or I could force the date to be in dd/mm/yyyy format?
That would certainly simplify matters.  Please try adjusting line 8 to look like this:

var match = resp.match(/^\s*(\d{1,2})\/(\d{1,2})\/(\d{4})\s*$/);
Thanks a heap.  Perfect.
Date validation in a dropdown calendar (date picker)