Compare Dates in ASP

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this might be easy, maybe not:

I have a form (well, several) with a date range (drop-downs for month, day, year) and in the .asp based page used to preview the form, i assemble the three drop-down Request.Form values to create a string that looks just like a date in format dd/mm/yyyy.. Obviously it would be good to validate the data from the form before processing to make sure people don’t give a higher date range in the FROM than in the TO date fields (which are drop-down boxes on the .html form). Does ASP recognize a pattern like dd/mm/yyyy. as anything in particular, such that I can test for one date being more recent than the other? or do I need to do some Javascript validation first? — say, in the .html page?

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I think you’re looking for the CDate() function

-Build a string from the individual values like so: strStartDate = Request.Form(“startDay”) & “/” & Request.Form(“startMonth”) & “/” & Request.Form(“startYear”)
(Do the same thing for your End date)
-Convert the date string into a date value: dteStartDate = CDate(strStartDate)
(Do the same thing with the End date string)
-Compare as necessary: If dteStartDate > dteEndDate Then…

Hope this helps – post back with any further questions

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thanks. CDate did the trick!

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(Edited by jscher2000 on 23-Apr-03 19:38. I think I had that backwards before.)

I think it might be a better user experience to validate prior to submission, but I can’t say I know the best syntax for that. A peek at my JavaScript book suggests something like this in your onSubmit event handler for the form:

If (Date.parse(TO) < Date.parse(FROM))
{
alert("Time travel is not permitted. Try again.");
return (false);
}

Date.parse(date-string) returns a value in milliseconds from 1 Jan 1970 00:00 GMT, so for all practical applications, you should always get a positive number. I don't know whether you need to feed it an actual time, or whether it will simply assume midnight in the absence of that information.

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