compare txtDate and systemDate

Hi! I have txtDate in form asp.net. First time I manual input date in txtDate (txtDate=”06.04.2016”). Program must automatically change Date in txtDate every day not depend from system date. For example:

Today               06.04.2016

Tomorrow          07.04.2016

After tomorrow   08.04.2016.

But every time run program must check txtDate with system date and compare it’s. if txtDate equal system date then program run else show message please check system date. Here I don’t want complete txtDate from system date. How I can solve this problem?