How to display calendar date in two textbox?

in that i have two fields date of birth and wedding day.
 
Date of Birth Textbox1 calendar
 
Wedding Day Textbox2
 

when i click the calendar that particular date to be displayed in texbox1 then i click the same calendar that particular date to be displayed in textbox2 Wedding day.

how to do using else condition.
 
how to do using one calendar.
 
for that please send the code in asp.net with c sharp.