Day of the Week

There is a much easier, buit-in way to get the day of the year for a given date, you have to be using Java 8, however. In order to use that, you must import java.time.LocalDate;

The following is the same method as in the code, however, it has been written using built-in way of obtaining the day of the year:

public static String getDay(int day, int month, int year) {
  LocalDate date = LocalDate.of(year, month, day);
  return date.getDayOfYear().name();
}

Despite of this, I thought it would be fun to make my own method, which uses Zeller's rule to calculate the day of the week for any given date.

Zeller's rule states:

where

• is the day of the week
  • 0 → Sunday
  • 1 → Monday
  • 2 → Tuesday
  • 3 → Wednesday
  • 4 → Thursday
  • 5 → Friday
  • 6 → Saturday
• is the day of the month
• is the month of the year
  • January → 11
  • February → 12
  • March → 1
  • April → 2
  • May → 3
  • June → 4
  • July → 5
  • August → 6
  • September → 7
  • October → 8
  • November → 9
  • December → 10
• is the number of decades in the century up to the year (i.e. year % 100)
  • When month is January or February, of the previous year is considered
• is the number of centuries up to the century (i.e. year / 100)
  • When month is January or February, of the previous year is considered

For some dates, there are cases where evaluates to a negative number. The rule provides a work-around for such a case as follows:

• Find the largest multiple of 7 that is less than or equal to
• Subtract this multiple of 7, from
• Let this value become the new