Add number to time

private void button1_Click(object sender, System.EventArgs e)
{
int dh1=System.DateTime.Now.Hour;
int dm1=System.DateTime.Now.Minute;
int ds1=System.DateTime.Now.Second;

int dh2=2;
int dm2=30;
int ds2=0;

int rh=dh1+dh2;
int rm=dm1+dm2;
int rs=ds1+ds2;

while(rh>=60)
{
rm=rm+1;
rs=rs-60;
}
while(rm>=60)
{
rh=rh+1;
rm=rm-60;
}
while(rh>12)
{
rh=rh-12;
}

textBox1.Text=rh.ToString()+":"+rm.ToString()+":"+rs.ToString();

}

private void button2_Click(object sender, System.EventArgs e)
{
System.Data.OleDb.OleDbConnection con = new System.Data.OleDb.OleDbConnection("provider=Microsoft.Jet.OleDb.4.0; data source=c:/i-scan/database.mdb");
con.Open();
string sql="select thour from ordinary where oid='1'";
System.Data.OleDb.OleDbCommand cmd = new System.Data.OleDb.OleDbCommand(sql,con);
System.Data.OleDb.OleDbDataReader rset = cmd.ExecuteReader();
if(rset.Read())
{

int dh1=System.DateTime.Now.Hour;
int dm1=System.DateTime.Now.Minute;
int ds1=System.DateTime.Now.Second;
MessageBox.Show(dh1.ToString());



string [ ] d2 = rset.GetValue(0).ToString().Split(':');

int rh=dh1+Convert.ToInt16(d2[0].ToString());
int rm=dm1+Convert.ToInt16(d2[1].ToString());
int rs=ds1+Convert.ToInt16(d2[2].ToString());

while(rh>=60)
{
rm=rm+1;
rs=rs-60;
}
while(rm>=60)
{
rh=rh+1;
rm=rm-60;
}
while(rh>12)
{
rh=rh-12;
}


string ltime;
if(dh1==0) dh1=12;

if (dh1>12 &&amp;amp; dh1<24)
{
dh1=dh1-12;
ltime=dh1.ToString()+":"+dm1.ToString()+":"+ds1.ToString()+":PM";
}
else
ltime=dh1.ToString()+":"+dm1.ToString()+":"+ds1.ToString()+":AM";

string lotime=rh.ToString()+":"+rm.ToString()+":"+rs.ToString();

con.Close();
con.Open();
MessageBox.Show(dh1.ToString());
sql="update ordinary set logintime='"+ ltime +"',logouttime='"+lotime +"' where oid='1'";
MessageBox.Show(sql);
System.Data.OleDb.OleDbCommand cmd1 = new System.Data.OleDb.OleDbCommand(sql,con);
cmd1.ExecuteNonQuery();
con.Close();
}
else
{
rset.Close();
con.Close();
}

}