ISO Week No's
Hi Just noticed that %ww% is creating the weekno's in American format. Is it possible to also get a option for us Europenans who are forced :) to use ISO standard. The ISO standard defines a week as a periode of 7 days starting with Monday and ending with Sunday. Week 1 in any year is the first such periode that contains at least 4 days from that year. This means for one thing that up to 3 days at the beginning of a year can be part of the last week (52 or 53) in the previous year, and up to 3 days at the end of a year can be part of week 1 in the following year. I am unsure what lanuage you are developing in but if it is .NET the following will provide a ISO result : /// <summary> /// Weeks the number_ entire4 day week rule. /// </summary> /// <param name="date">The date.</param> /// <returns></returns> private int WeekNumber_Entire4DayWeekRule(DateTime date) { // Calculates the ISO 8601 Week Number // In this scenario the first day of the week is monday, // and the week rule states that: // <...> the first calendar week of a year is the one // that includes the first Thursday of that year and // <...> the last calendar week of a calendar year is // the week immediately preceding the first // calendar week of the next year. // The first week of the year may thus start in the // preceding year const int JAN = 1; const int DEC = 12; const int LASTDAYOFDEC = 31; const int FIRSTDAYOFJAN = 1; const int THURSDAY = 4; bool ThursdayFlag = false; // Get the day number since the beginning of the year int DayOfYear = date.DayOfYear; // Get the numeric weekday of the first day of the // year (using sunday as FirstDay) int StartWeekDayOfYear = (int)(new DateTime(date.Year, JAN, FIRSTDAYOFJAN)).DayOfWeek; int EndWeekDayOfYear = (int)(new DateTime(date.Year, DEC, LASTDAYOFDEC)).DayOfWeek; // Compensate for the fact that we are using monday // as the first day of the week if( StartWeekDayOfYear == 0) StartWeekDayOfYear = 7; if( EndWeekDayOfYear == 0) EndWeekDayOfYear = 7; // Calculate the number of days in the first and last week int DaysInFirstWeek = 8 - (StartWeekDayOfYear ); int DaysInLastWeek = 8 - (EndWeekDayOfYear ); // If the year either starts or ends on a thursday it will have a 53rd week if (StartWeekDayOfYear == THURSDAY || EndWeekDayOfYear == THURSDAY) ThursdayFlag = true; // We begin by calculating the number of FULL weeks between the start of the year and // our date. The number is rounded up, so the smallest possible value is 0. int FullWeeks = (int) Math.Ceiling((DayOfYear - (DaysInFirstWeek))/7.0); int WeekNumber = FullWeeks; // If the first week of the year has at least four days, then the actual week number for our date // can be incremented by one. if (DaysInFirstWeek >= THURSDAY) WeekNumber = WeekNumber +1; // If week number is larger than week 52 (and the year doesn't either start or end on a thursday) // then the correct week number is 1. if (WeekNumber > 52 && !ThursdayFlag) WeekNumber = 1; // If week number is still 0, it means that we are trying to evaluate the week number for a // week that belongs in the previous year (since that week has 3 days or less in our date's year). // We therefore make a recursive call using the last day of the previous year. if (WeekNumber == 0) WeekNumber = WeekNumber_Entire4DayWeekRule( new DateTime(date.Year-1, DEC, LASTDAYOFDEC)); return WeekNumber; } Thanks Murtagh
Hi Just noticed that %ww% is creating the weekno's in American format. Is it possible to also get a option for us Europenans who are forced :) to use ISO standard. The ISO standard defines a week as a periode of 7 days starting with Monday and ending with Sunday. Week 1 in any year is the first such periode that contains at least 4 days from that year. This means for one thing that up to 3 days at the beginning of a year can be part of the last week (52 or 53) in the previous year, and up to 3 days at the end of a year can be part of week 1 in the following year. I am unsure what lanuage you are developing in but if it is .NET the following will provide a ISO result : /// <summary> /// Weeks the number_ entire4 day week rule. /// </summary> /// <param name="date">The date.</param> /// <returns></returns> private int WeekNumber_Entire4DayWeekRule(DateTime date) { // Calculates the ISO 8601 Week Number // In this scenario the first day of the week is monday, // and the week rule states that: // <...> the first calendar week of a year is the one // that includes the first Thursday of that year and // <...> the last calendar week of a calendar year is // the week immediately preceding the first // calendar week of the next year. // The first week of the year may thus start in the // preceding year const int JAN = 1; const int DEC = 12; const int LASTDAYOFDEC = 31; const int FIRSTDAYOFJAN = 1; const int THURSDAY = 4; bool ThursdayFlag = false; // Get the day number since the beginning of the year int DayOfYear = date.DayOfYear; // Get the numeric weekday of the first day of the // year (using sunday as FirstDay) int StartWeekDayOfYear = (int)(new DateTime(date.Year, JAN, FIRSTDAYOFJAN)).DayOfWeek; int EndWeekDayOfYear = (int)(new DateTime(date.Year, DEC, LASTDAYOFDEC)).DayOfWeek; // Compensate for the fact that we are using monday // as the first day of the week if( StartWeekDayOfYear == 0) StartWeekDayOfYear = 7; if( EndWeekDayOfYear == 0) EndWeekDayOfYear = 7; // Calculate the number of days in the first and last week int DaysInFirstWeek = 8 - (StartWeekDayOfYear ); int DaysInLastWeek = 8 - (EndWeekDayOfYear ); // If the year either starts or ends on a thursday it will have a 53rd week if (StartWeekDayOfYear == THURSDAY || EndWeekDayOfYear == THURSDAY) ThursdayFlag = true; // We begin by calculating the number of FULL weeks between the start of the year and // our date. The number is rounded up, so the smallest possible value is 0. int FullWeeks = (int) Math.Ceiling((DayOfYear - (DaysInFirstWeek))/7.0); int WeekNumber = FullWeeks; // If the first week of the year has at least four days, then the actual week number for our date // can be incremented by one. if (DaysInFirstWeek >= THURSDAY) WeekNumber = WeekNumber +1; // If week number is larger than week 52 (and the year doesn't either start or end on a thursday) // then the correct week number is 1. if (WeekNumber > 52 && !ThursdayFlag) WeekNumber = 1; // If week number is still 0, it means that we are trying to evaluate the week number for a // week that belongs in the previous year (since that week has 3 days or less in our date's year). // We therefore make a recursive call using the last day of the previous year. if (WeekNumber == 0) WeekNumber = WeekNumber_Entire4DayWeekRule( new DateTime(date.Year-1, DEC, LASTDAYOFDEC)); return WeekNumber; } Thanks Murtagh