for data sharing in ASP.NET you can find various state-full objects. for your purpose it will be better to use session object.
if you only require to pass date to next page. write following on page 1
Session["page1_date"] = pg1_lbl_date.Text;
now on load of page2 you can check that if the page is not post back and session is not empty then get date from session and display on page2.
i.e
private string page1_date_value = stirng.Empty;
Page_Load(object sender, EventArgs e)
{
if(Session["page1_date"] != null)
{
page1_date_value = Session["page1_date"];
}
}
this way you can get value on page2.
other than using session you can study QueryString as well.