validation problem in two date

well dude.. for example if you have two textboxes to enter "Date of Birth" & "Date of Joining" and you
want the user to enter the date of birth which should have to be the earlier than Date of Joining.
I.e. user was born on 12 feb 1989 and he joined your office etc on 12th may 2013... so you can use
compare validators to do this.

see the code below which might help you to clarify what i meant to say.

<asp:comparevalidator id="Validator1" runat="server" Display = "None" ControlToCompare="txtDateofBirth" ControlToValidate="txtDateofJoining" ErrorMessage="Date of Birth must be before Date of Joining." Operator="GreaterThan" Type="Date" ></asp:comparevalidator> 

in the above line of code validator will check the value of joining date with DOB and will show the error message
if user enters the date of birth as of 2013 & date of joining as of 1989.

Regards.

You can have your markup as something like this

<asp:textbox id="startDate" runat="server" xmlns:asp="#unknown"></asp:textbox>
       <asp:textbox id="endDate" runat="server" xmlns:asp="#unknown"></asp:textbox>
       <asp:customvalidator id="cv" runat="server" validationgroup="vg" clientvalidationfunction="validateYears" errormessage="invalid date" display="None" xmlns:asp="#unknown"></asp:customvalidator>
       <asp:button id="btn" runat="server" text="Click" validationgroup="vg" xmlns:asp="#unknown" />
       <asp:validationsummary id="vs" runat="server" validationgroup="vg" showmessagebox="true" showsummary="false" xmlns:asp="#unknown" />

and add a js validation method

function validateYears(source, args) {
            startYear = new Date(document.getElementById("startDate").value);
            endYear = new Date(document.getElementById("endDate").value);
            alert(endYear.getFullYear() - startYear.getFullYear() >= 20);
            args.IsValid = endYear.getFullYear() - startYear.getFullYear() >= 20;            
        }

the function here gets the difference in years and validates for a difference of 20 years, you might also want to consider difference in months or days.

However, i would not recommed using text boxes for dates as users may use multiple ways to enter a date