Develop Reference

How calculate if a Date is 6 month later birthdate in C#

how can I calculate if a date (in DateTime format) is 6 month later or not from my BirthDate (in DateTime format)?

Use DateTime AddMonth method
https://msdn.microsoft.com/ru-ru/library/system.datetime.addmonths(v=vs.110).aspx
var dat = new DateTime(2015, 12, 31);
var dat2 = new DateTime(2015, 12, 31);
if (dat.AddMonths(6) < dat2) { ... }

You should use DateTime.AddMonths :
DateTime dt;
DateTime birthDate;
if (dt <= birthDate.AddMonths(6))
{
}

enter your birth date, calculate your next birthday and compare the dates,
var born = new DateTime(1900, 02, 01);
var checkdate = DateTime.Now;
var nextBirthday = new DateTime(DateTime.Now.Year, born.Month, born.Day);
if (nextBirthday < DateTime.Now)
{
nextBirthday = new DateTime(DateTime.Now.Year + 1, born.Month, born.Day);
}
if (checkdate.AddMonths(6) < nextBirthday)
{
Console.WriteLine("date is 6 months later then birthday");
}
else
{
Console.WriteLine("wait for it");
}

DateTime birthDate=new DateTime(year,month,day);
DateTime dateToCompare = new DateTime(year, month, day);
if(dateToCompare >= birthdate.AddMonths(6))
{
//DoSomething
}

You could calculte the difference between dates using Subtract method and calculate how many months you have between these dates, for sample:
DateTime birthDay = /* some date */;
DateTime someDate = /* some date */;
var months = someDate.Subtract(birthDay).Days / (365.25 / 12);
This answer provides a good helper for Dates:
https://stackoverflow.com/a/33287670/316799

C# datetime scope

Assuming I can not change service that returns data, I am left with
var date = "20140231";
var scope = DateTime.ParseExact(date, "yyyyMMdd", CultureInfo.CurrentCulture);
Clearly "20140231" is lazy way of saying end of February. What is the cleanest way to get last date of February with input of "20140231"?
There is 1 constraint - this should work with .net 2.0.

string date = "20140231";
DateTime result;
int year = Convert.ToInt32(date.Substring(0, 4));
int month = Convert.ToInt32(date.Substring(4, 2));
int day = Convert.ToInt32(date.Substring(6, 2));
result = new DateTime(year, month, Math.Min(DateTime.DaysInMonth(year, month), day));

February can have only 28 or 29 days depends on current year is a leap year or not.
It can't have 30 or 31 days in any year. That's why you can't parse your 20140231 string successfully.
You can clearly get the last day of February like;
DateTime lastDayOfFebruary = (new DateTime(2014, 2, 1)).AddMonths(1).AddDays(-1);
If your service always get year as a first 4 character, you can use .Substring() to get year and pass DateTime constructor as a year.
var date = "20140231";
string year = date.Substring(0, 4);
DateTime lastDayOfFebruary = (new DateTime(int.Parse(year), 2, 1)).AddMonths(1).AddDays(-1);

You could create a while, cut the date in pieces, and keep subtracting one from the day part until it is a valid date. This should really be fixed on the entry side though.
Try this:
var date = "20140231";
DateTime scope;
bool dateValid = DateTime.TryParseExact(date, "yyyyMMdd", CultureInfo.CurrentCulture, DateTimeStyles.None, out scope);
while (!dateValid)
{
string yearMonth = date.Substring(0, 4);
int day = Convert.ToInt32(date.Substring(6, 2));
if (day > 1)
{
day--;
}
else
{
break;
}
date = yearMonth + day.ToString().PadLeft(2, '0');
dateValid = DateTime.TryParseExact(date, "yyyyMMdd", CultureInfo.CurrentCulture, DateTimeStyles.None, out scope);
}

Get days of week between two selected dates

I have two datetimepickers. So I want to get the days of the week between the selected values.
Example: date1 = 14/1/2015 and date2 = 17/1/2015
So the result should be: days = Wed. Thu. Fri. Sat.

You want to get the DayOfWeeks of all DateTimes between two dates?
int daysDiff = (date2 - date1).Days;
List<DayOfWeek> days = Enumerable.Range(0, daysDiff + 1) // +1 because you want to include start and end date
.Select(d => date1.AddDays(d).DayOfWeek)
.ToList();
You need to add using System.Linq;

You can easily iterate your DateTime values like;
var dt1 = new DateTime(2015, 1, 14);
var dt2 = new DateTime(2015, 1, 17);
while (dt2 >= dt1)
{
Console.WriteLine(dt1.DayOfWeek);
dt1 = dt1.AddDays(1);
}
Result will be;
Wednesday
Thursday
Friday
Saturday
If you wanna their abbreviated day names as Wed, Thu, Fri, Sat, you can use "ddd" custom format specifier with a english-based culture (like InvariantCulture) like;
var dt1 = new DateTime(2015, 1, 14);
var dt2 = new DateTime(2015, 1, 17);
while (dt2 >= dt1)
{
Console.WriteLine(dt1.ToString("ddd", CultureInfo.InvariantCulture));
dt1 = dt1.AddDays(1);
}

Another alternative, which includes non-usual use of a for-loop and the yield return statement:
void Main()
{
var daysOfWeek = DaysBetween(
new DateTime(2015, 1, 14),
new DateTime(2015, 1, 17));
Console.WriteLine(
String.Join(", ", daysOfWeek.Select(d => d.ToString().Substring(0, 3))));
// prints: Wed, Thu, Fri, Sat
}
IEnumerable<DayOfWeek> DaysBetween(DateTime start, DateTime end)
{
for (var dateTime = start; dateTime <= end; dateTime = dateTime.AddDays(1))
{
yield return dateTime.DayOfWeek;
}
}

How to calculate financial year start and end dates from financial year's month end value?

I have a financial year's month end value 2.
How would i calculate the financial year DateTime startDate and DateTime endDate from that value?

You can do:
DateTime startDate = new DateTime(DateTime.Today.Year, 2, 1); // 1st Feb this year
DateTime endDate = new DateTime(DateTime.Today.Year+1, 2, 1).AddDays(-1); // Last day in January next year
Does that solve your problem?

I assume you mean Feb by 2.
This code should do this:
DateTime start = new DateTime(2010,2,1);
DateTime end = start.AddMonths(12).AddDays(-1);
Console.WriteLine(start);
Console.WriteLine(end);
Output:
01-Feb-10 12:00:00 AM
31-Jan-11 12:00:00 AM

Here is my version for calculating the Fiscal Year Start Date. It checks the StartMonth against the current month, and will adjust the year.
private DateTime? FiscalYearStartDate() {
int fyStartMonth = 2;
var dte = new DateTime(DateTime.Today.Year, fyStartMonth, 1); // 1st April this year
if (DateTime.Today.Month >= fyStartMonth) {
//Do nothing, since this is the correct calendar year for this Fiscal Year
} else {
//The FY start last calendar year, so subtract a year
dte = dte.AddYears(-1);
}
return dte;
}
You can easily calculate the End Date like others have done, by adding +1 Year, and then subtracting 1 Day (thanks to Johannes Rudolph).
DateTime endDate = new DateTime(DateTime.Today.Year+1, 2, 1).AddDays(-1);

If your current date is 14/01/2021
Then the Indian financial Year is 01/04/2020 to 31/03/2021
Use the following code for perfect output.
DateTime CurrentDate = DateTime.Now;
int CurrentMonth = CurrentDate.Month;
if (CurrentMonth >= 4)//4 is the first month of the financial year.
{
txtFromDate.Text = new DateTime(CurrentDate.Year, 4, 1).ToString(CS.ddMMyyyy);
txtToDate.Text = new DateTime(CurrentDate.Year + 1, 4, 1).AddDays(-1).ToString(CS.ddMMyyyy);
}
else
{
txtFromDate.Text = new DateTime(CurrentDate.Year - 1, 4, 1).ToString(CS.ddMMyyyy);
txtToDate.Text = new DateTime(CurrentDate.Year, 4, 1).AddDays(-1).ToString(CS.ddMMyyyy);
}

public static (DateTime, DateTime) GetCurrentFinacialYearDateRange()
{
if(DateTime.Now.Month >= 7)
{
DateTime startDate = new DateTime(DateTime.Today.Year, 7, 1); // 1st July this year
DateTime endDate = new DateTime(DateTime.Today.Year + 1, 7, 1).AddDays(-1); // Last day in June next year
return (startDate, endDate);
}
else
{
DateTime startDate = new DateTime(DateTime.Today.Year-1, 7, 1); // 1st July this year
DateTime endDate = new DateTime(DateTime.Today.Year, 7, 1).AddDays(-1); // Last day in June next year
return (startDate, endDate);
}
}

How to check if a DateTime range is within another 3 month DateTime range

Hi I have a Start Date and End Date per record in a db.
I need to check to see where the time period falls in a 2 year period broken into two lots of quarters then display what quarters each record falls into.
Quarter 1 includes June 09, Jul 09, Aug 09
Quarter 2 includes Sept 09, Oct 09, Nov 09
Quarter 3 includes Dec 09, Jan 10, Feb 10
Quarter 4 includes Mar 10, Apr 10, May 10
Quaretr 5 includes Jun 10, Jul 10...
e.g. 01/10/09 - 01/06/10 would fall into quarters 2, 3, 4 & 5
I am very new to .NET so any examples would be much appreciated.

This should work for you also.
class Range
{
public DateTime Begin { get; private set; }
public DateTime End { get; private set; }
public Range(DateTime begin, DateTime end)
{
Begin = begin;
End = end;
}
public bool Contains(Range range)
{
return range.Begin >= Begin && range.End <= End;
}
}
and then to use it
List<Range> ranges = new List<Range>();
ranges.Add(new Range(DateTime.Now, DateTime.Now.AddMonths(3)));
ranges.Add(new Range(DateTime.Now.AddMonths(3), DateTime.Now.AddMonths(6)));
Range test = new Range(DateTime.Now.AddMonths(1), DateTime.Now.AddMonths(2));
var hits = ranges.Where(range => range.Contains(test));
MessageBox.Show(hits.Count().ToString());

You would call IntervalInQuarters as follows:
IntervalInQuarters(new DateTime(2007, 10, 10), new DateTime(2009, 10, 11));
The function returns a list of quarter start dates. Note that the range of quarters searched is defined within the function itself. Please edit as appropriate for your situation. They key point is to make sure the interval/quarter intersection logic is right.
private List<DateTime> IntervalInQuarters(DateTime myStartDate, DateTime myEndDate)
{
DateTime quarterStart = new DateTime(2006, 06, 01);
DateTime nextQuarterStart = new DateTime(2006, 09, 01);
DateTime finalDate = new DateTime(2011, 01, 01);
List<DateTime> foundQuarters = new List<DateTime>();
while (quarterStart < finalDate)
{
// quarter intersects interval if:
// its start/end date is within our interval
// our start/end date is within quarter interval
DateTime quarterEnd = nextQuarterStart.AddDays(-1);
if (DateInInterval(myStartDate, quarterStart, quarterEnd) ||
DateInInterval(myEndDate, quarterStart, quarterEnd) ||
DateInInterval(quarterStart, myStartDate, myEndDate) ||
DateInInterval(quarterEnd, myStartDate, myEndDate))
{
foundQuarters.Add(quarterStart);
}
quarterStart = nextQuarterStart;
nextQuarterStart = nextQuarterStart.AddMonths(3);
}
return foundQuarters;
}
private bool DateInInterval(DateTime myDate, DateTime intStart, DateTime intEnd)
{
return ((intStart <= myDate) && (myDate <= intEnd));
}

private void Form1_Load(object sender, EventArgs e)
{
DateTime[,] ranges = new DateTime[3,2];
//Range 1 - Jan to March
ranges[0, 0] = new DateTime(2010, 1, 1);
ranges[0, 1] = new DateTime(2010, 3, 1);
//Range 2 - April to July
ranges[1, 0] = new DateTime(2010, 4, 1);
ranges[1, 1] = new DateTime(2010, 7, 1);
//Range 3 - March to June
ranges[2, 0] = new DateTime(2010, 3, 1);
ranges[2, 1] = new DateTime(2010, 6, 1);
DateTime checkDate = new DateTime(2010, 4, 1);
string validRanges = string.Empty;
for (int i = 0; i < ranges.GetLength(0); i++)
{
if (DateWithin(ranges[i,0], ranges[i,1], checkDate))
{
validRanges += i.ToString() + " ";
}
}
MessageBox.Show(validRanges);
}
private bool DateWithin(DateTime dateStart, DateTime dateEnd, DateTime checkDate)
{
if (checkDate.CompareTo(dateStart) < 0 || checkDate.CompareTo(dateEnd) > 0)
{
return false;
}
return true;
}

You may have to take a look at: http://msdn.microsoft.com/en-us/library/03ybds8y(v=VS.100).aspx
This may start you up
FindQuarter(DateTime startDate, DateTime endDate) // 01-10-09, 01-06-10
{
startDateQuarter = GetQuarter(startDate.Month); // 2
endDateQuarter = GetQuarter(endDate.Month); // 1
endDateQuarter += (endDate.Year - startDate.Year) * 4; // 5
// fill up startDateQuarter to endDateQuarter into a list
// and return it // 2,3,4,5
}
GetQuarter(int month) // 6
{
int quarter;
// check the month value and accordingly assign one of the basic quarters
// using if-else construct ie, if(month>=6 && month<=8){ quarter = 1 };
return quarter; // 1
}
Instead of GetQuarter() method, you can also use a dictionary to store your month to quarter mappings
Dictionary<int, int> quarter = new Dictionary<int, int>();
quarter.Add(1,1); //of the format Add(month,quarter)
quarter.Add(2,1);
...
Now instead of GetQuarter(someDate.Month); you can use quarter[someDate.Month];

If you want to compare two dates you should find out the first day of the quarter corresponds every of this dates, then you can compare this two dates:
using System;
namespace DataTime {
class Program {
static int GetQuarter (DateTime dt) {
int Month = dt.Month; // from 1 to 12
return Month / 3 + 1;
}
static DateTime GetQuarterFirstDay (DateTime dt) {
int monthsOfTheFirstDayOfQuarter = (GetQuarter (dt) - 1) * 3 + 1;
return new DateTime(dt.Year, monthsOfTheFirstDayOfQuarter, 1);
// it can be changed to
// return new DateTime(dt.Year, (dt.Month/3)*3 + 1, 1);
}
static void Main (string[] args) {
DateTime dt1 = new DateTime (2009, 6, 9),
dt2 = new DateTime (2009, 7, 9),
dt3 = new DateTime (2009, 8, 9),
dt4 = new DateTime (2009, 8, 9);
Console.WriteLine ("dt1={0}", dt1.AddMonths (1));
Console.WriteLine ("dt2={0}", dt2.AddMonths (1));
Console.WriteLine ("dt3={0}", dt3.AddMonths (1));
DateTime startDate = DateTime.Now,
endDate1 = startDate.AddMonths(24).AddDays(1),
endDate2 = startDate.AddMonths(24).AddDays(-1),
endDate3 = startDate.AddMonths(28);
Console.WriteLine ("Now we have={0}", startDate);
Console.WriteLine ("endDate1={0}", endDate1);
Console.WriteLine ("endDate2={0}", endDate2);
Console.WriteLine ("endDate3={0}", endDate3);
Console.WriteLine ("GetQuarterFirstDay(startDate)={0}", GetQuarterFirstDay (startDate));
Console.WriteLine ("GetQuarterFirstDay(endDate1)={0}", GetQuarterFirstDay (endDate1));
Console.WriteLine ("GetQuarterFirstDay(endDate2)={0}", GetQuarterFirstDay (endDate2));
Console.WriteLine ("GetQuarterFirstDay(endDate3)={0}", GetQuarterFirstDay (endDate3));
if (DateTime.Compare (GetQuarterFirstDay (endDate2), GetQuarterFirstDay (startDate).AddMonths (24)) > 0)
Console.WriteLine ("> 2 Yeas");
else
Console.WriteLine ("<= 2 Yeas");
if (DateTime.Compare (GetQuarterFirstDay (endDate3), GetQuarterFirstDay (startDate).AddMonths (24)) > 0)
Console.WriteLine ("> 2 Yeas");
else
Console.WriteLine ("<= 2 Yeas");
}
}
}
produce
dt1=09.07.2009 00:00:00
dt2=09.08.2009 00:00:00
dt3=09.09.2009 00:00:00
Now we have=22.04.2010 11:21:45
endDate1=23.04.2012 11:21:45
endDate2=21.04.2012 11:21:45
endDate3=22.08.2012 11:21:45
GetQuarterFirstDay(startDate)=01.04.2010 00:00:00
GetQuarterFirstDay(endDate1)=01.04.2012 00:00:00
GetQuarterFirstDay(endDate2)=01.04.2012 00:00:00
GetQuarterFirstDay(endDate3)=01.07.2012 00:00:00
<= 2 Yeas
> 2 Yeas
EDITED: I fixed an error from the first version. Now it should works correct.