Today Is Nth Day of Year

Today is nth day of year

Calendar calendar = Calendar.getInstance();
int dayOfYear = calendar.get(Calendar.DAY_OF_YEAR);  

Or using Joda-API

DateTime dt = new DateTime();  
int dayOfYear = dt.getDayOfYear();  

If you need 'th' part, use switch statement

switch (dayOfYear > 20 ? (dayOfYear % 10) : dayOfYear) {
            case 1:  return dayOfYear + "st";
                     break;
            case 2:  return dayOfYear + "nd";
                     break;
            case 3:  return dayOfYear + "rd";
                     break;
            default:  return dayOfYear + "th";
                     break;   
} 

Get the nth day of a year

It looks like the idea you're going for is a recursive approach that decrements by month.

static int dayNumberInYear(int day, Month month, int year)
    {
      if(!month.equals(Month.JANUARY)) {
        return day + dayNumberInYear(numberOfDaysInMonth(month.minus(1), year), month.minus(1), year);
      } else {
        return day;
      }
}

Note that in this recursive approach, the base case is that it's January and we simply return the current day in January. Otherwise we add the day of the current month and then all the days in every prior month.

It could also be done as a for-loop.

static int dayNumberInYearByLoop(int day, Month month, int year) {
  int totalDays = day;
  for (int i = month.getValue();i>1;i--) {
    totalDays += numberOfDaysInMonth(Month.of(i), year);
  }
  return totalDays;
}

You can mess around with my code here: https://repl.it/repls/ConcreteDarkgreenSequence

How to get day of year number in Java for a specific date object?

Calendar#get(Calendar.DAY_OF_YEAR);

Get DateTime of the next nth day of the month

Why not just do?

private DateTime GetNextDate(DateTime dt, int DesiredDay)
{
    if (DesiredDay >= 1 && DesiredDay <= 31)
    {
        do
        {
            dt = dt.AddDays(1);
        } while (dt.Day != DesiredDay);
        return dt.Date;
    }
    else
    {
        throw new ArgumentOutOfRangeException();
    }     
}

Calculate the N th day of the previous year

You could do:

from datetime import datetime, timedelta

date_string = '2020-03-09'

# Parse the string to a datetime.date object
date = datetime.strptime(date_string, '%Y-%m-%d')

# Get the number N of the day in the year
N = date.timetuple().tm_yday

# Take 1st of january of last year and add N-1 days
N_last_year = (
    date.replace(year=date.year-1, month=1, day=1) + 
    timedelta(days=N-1)
)

print(N_last_year.date())

Or, another funny solution based on leap years. It is based on the fact that the Nth day of last year is the same as this year's, except if the date is after 29th february and there is a leap year somewhere.

from datetime import datetime, timedelta

def leap(year: int) -> bool:
    # Returns True if year is a leap year, False otherwise
    return (year % 4 == 0 and year % 100 != 0) or (year % 400 == 0)

date_string = '2020-03-09'

# Parse the string to a datetime.date object
date = datetime.strptime(date_string, '%Y-%m-%d')

# Get the number N of the day in the year
N = date.timetuple().tm_yday

date_last_year = date.replace(year=date.year-1)

# Do the cool thing
if date.month >= 3:
    if leap(date.year):
        date_last_year += timedelta(days=1)
    elif leap(date.year-1):
        date_last_year += timedelta(days=-1)

print(date_last_year.date())

Calculate number of days until nth day of month

Perhaps this can be simplified but I'd break it down into the following logic:

• If the day - i.e. the 23rd - is less than or equal to 20, then take the difference between the two.
• Otherwise, calculate the 20th day of the next month, and take the difference.

Something like this:

=IF(DAY(A2)<=20,20-DAY(A2),DATE(YEAR(EOMONTH(A2,1)),MONTH(EOMONTH(A2,1)),20)-A2)

JavaScript calculate the day of the year (1 - 366)

Following OP's edit:

var now = new Date();var start = new Date(now.getFullYear(), 0, 0);var diff = now - start;var oneDay = 1000 * 60 * 60 * 24;var day = Math.floor(diff / oneDay);console.log('Day of year: ' + day);

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