Write below code:-
public DateTime GetFirstDayofQuarter(DateTime dt)
{
int current_quarter = (dt.Month - 1) / 3 + 1;
DateTime dtFirstDay = new DateTime(dt.Year, 3 * current_quarter - 2, 1);
return dtFirstDay;
}
To test above function:-
Response.Write("First Day of Quarter is for " + DateTime.Now.ToShortDateString() + " : " + GetFirstDayofQuarter
(DateTime.Now) + "<br/>"); //8-april-2015
Response.Write("First Day of Quarter is for " + DateTime.Now.AddMonths(5).ToShortDateString() + " : " +
GetFirstDayofQuarter(DateTime.Now.AddMonths(5)) + "<br/>"); //8-september-2015
Output:-
Response.Write("First Day of Quarter is for " + DateTime.Now.ToShortDateString() + " : " + GetFirstDayofQuarter
(DateTime.Now) + "<br/>");
Response.Write("First Day of Quarter is for " + DateTime.Now.AddMonths(5).ToShortDateString() + " : " +
GetFirstDayofQuarter(DateTime.Now.AddMonths(5)) + "<br/>");