//
// CogersMeetingDate.js
//
// Adrian Redgers created this. All rights reserved, no responsibility accepted. (c) 11 October 2003
//
// Routine to display the date of Cogers meetings in the form: "Tuesday, 11th October 2003"
//
//
//
// To use:
// * Save this file as: CogersMeetingDate.js near the HTML that will display the date of the meeting.
//
// * In that HTML file insert the following line between the tags:
//
// NOTE: make sure the path is correct if CogersMeetingDate.js is in a different directory
// e.g. if in the directory above then "../CogersMeetingDate.js"
// NOTE: use because the self-closing form: doesn't work with Netscape.
//
// * At the point where you want to print the next meeting date for a club insert the following:
//
//
// * Allowed clubs are: DINING, CITY, WESTMINSTER, WARE, SYLVANS
//
//
//
// Advanced:
// * If a club meeting is cancelled then edit IsClubHoliday()
//
// * If a club meeting is moved within a month then edit MoveClubMeeting() with the details
//
// * If another special public holiday is announced then add it to the IsSpecialBank() function at the
// bottom of this file.
// NOTE: you may have to amend another function if that holiday is moved - e.g Spring Bank holiday 2002
//
// * To add another club, add it to the enumerated list below, and to the CogersMeetingDate(clubName, theDate) function.
// NOTE Watch out for *last* xDay of the month (e.g. the last Friday) versus nth xDay (e.g the 2nd Monday)
// NOTE watch out for the Sylvans - IsClubHoliday()
//
// * To get the next meeting on or after a given date, (e.g. 11 October, 2003) insert the following:
//
// NOTE the comma between 'October' and '2003'
//
// * To get the *following* meeting *after* a given date insert the following:
//
//
//
//
//
// Enumerated list of clubs
//
SYLVANS = 1;
WESTMINSTER = 2;
CITY = 3;
DINING = 4;
WARE = 5;
UNIVERSITY = 6;
CAMBRIDGE = 7
//
//
// Useful lists: days [0=Sunday, 6=Saturday], months [0=January, 11=December]
// Would like to put the month-days here, but February cocks it up if we use it for other years.
//
_days = ["Sunday", "Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday"];
_months = ["January", "February", "March", "April", "May", "June", "July", "August", "September", "October", "November", "December"];
//
// Get today's date
//
today = new Date(); // Set to today by default
//
// Get the date of the next meeting for the given club - today if before 8pm
//
function NextCogersMeetingDate(theClub)
{
return( DisplayDate(CogersMeetingDate(theClub, new Date(today))) );
}
//
// Get the following month's meeting date *after* the given date.
// If the given date is already a meeting date then skip to the next month.
// NOTE: this doesn't display the date - if you want to diplay it use the DisplayDate() as shown above.
//
function FollowingMeetingDate(theClub, theDate)
{
theDate.setHours(21); // Force a skip to the next meeting
return(CogersMeetingDate(theClub, theDate));
}
//
// Get the date of the meeting for the given club *on-or-after* the given date
// NOTE: this doesn't display the date - if you want to diplay it use the DisplayDate() as shown above.
//
function CogersMeetingDate(theClub, theDate)
{
var month = theDate.getMonth()+1; // Set months from 1-12 to make it easier for me to understand
var year = theDate.getFullYear();
var monthYearVec = new Array(2); // vec[0] = month , vec[1] = year
monthYearVec[0] = month;
monthYearVec[1] = year;
var returnDateVec = new Array(3); // Return a vector of the date, plus moved-flag, plus moved from date
// vec[0] = actual date of meeting,
// vec[1] = meeting-was-moved flag : true or false
// vec[3] = moved-from date
//
// If there's a meeting today we want to have it as the *next* meeting
// but not if we have just missed it (time > 8pm)
//
// Reset the time of the given date to midnight
// to ensure a *calculated* meeting-date of 'today' is at least as big as a
// *given* date of 'today'
//
if(theDate.getHours() < 20)
{
theDate.setMinutes(0);
theDate.setHours(0);
theDate.setSeconds(0);
theDate.setMilliseconds(0);
}
var saveDate = new Date(theDate); // Save the given date to check 'on-or-after' it
var nth = 0; // nth xDay of the month, e.g. "2nd Tuesday of the month"
var xDay = 0; // 0=Sunday <= xDay <= 6=Saturday
var last = false; // Not *nth* but *last* xDay of the month e.g. "last Friday of the month"
if(DINING == theClub)
{
xDay = 5; // Cogers Dining club meets on the *last* Friday of the month
last = true;
} else if(WARE == theClub)
{
nth = 3; // Ware Cogers meets on 3rd Tuesday of the month
xDay = 2;
} else if(CITY == theClub)
{
nth = 2; // City of London Cogers meets on 2nd Monday of the month
xDay = 1
} else if(WESTMINSTER == theClub)
{
nth = 4; // Westiminster Cogers meets on 4th Wednesday of the Month
xDay = 3;
} else if(SYLVANS == theClub)
{
nth = 1; // Sylvans meet on 1st Monday of the Month
xDay = 1;
} else if(UNIVERSITY == theClub)
{
nth = 3; // UoL Cogers meets on 3rd Wednesday of the Month
xDay = 3;
}
//
// Calculate the date of the next meeting from the given date.
// If the calculated date is earlier than the given date, or if the calculated day is a holiday
// then skip on to the following month.
//
do // Step past holidays and dates before the given date
{
if(last)
theDate = LastXday(xDay, month, year);
else
theDate = NthXday(nth, xDay, month, year);
returnDateVec[1] = false; // Initially guess meeting was not moved
returnDateVec[2] = new Date(theDate); // Initial date of meeting
theDate = MoveClubMeeting(theClub, theDate);
// Move the meeting date if necessary
returnDateVec[0] = new Date(theDate); // Actual meeting date - was it moved?
if(returnDateVec[0].getDay() != returnDateVec[2].getDay())
{
returnDateVec[1] = true; // yes, the meeting was moved
}
monthYearVec[0] = month;
monthYearVec[1] = year;
monthYearVec = NextMonth(monthYearVec); // Increment to the next month (and year if necessary)
month = monthYearVec[0];
year = monthYearVec[1];
} while( (theDate < saveDate) || IsHoliday(theDate) || IsClubHoliday(theClub, theDate));
return(returnDateVec);
}
//
// Return true if the club is having a break at this time
//
function IsClubHoliday(theClub, theDate)
{
// The Sylvans meet every month now
// if(SYLVANS == theClub)
// {
// var month = theDate.getMonth()+1; // Set month to [1, 12] for clarity.
// if((3 < month) && (10 > month)) // The Sylvans only meet from October to March
// return(true);
// }
return(false);
}
//
// Move the date of a meeting within a month if necessary
//
function MoveClubMeeting(theClub, theDate)
{
//
// Sylvans meeting on 17th November 2003 was moved to 18th November
//
if(SYLVANS == theClub)
{
if( (2003 == theDate.getFullYear()) && (11 == theDate.getMonth()+1) // I prefer my months numbered 1-12, not 0-11
&& (17 == theDate.getDate()) )
{
theDate.setDate(18);
}
}
//
// City meeting on 12th April 2004 was moved to 13th April
//
if(CITY == theClub)
{
if( (2004 == theDate.getFullYear()) && (4 == theDate.getMonth()+1) // I prefer my months numbered 1-12, not 0-11
&& (12 == theDate.getDate()) )
{
theDate.setDate(13);
}
}
return(theDate);
}
//
// Display the given date, e.g. Thursday, 9th October 2003
//
function DisplayDate(dateVec)
{
var theDate = dateVec[0];
document.write( _days[theDate.getDay()] + ', ' + theDate.getDate() +OrdinalSuffix(theDate.getDate())+ ' '
+ _months[theDate.getMonth()] + ' ' + theDate.getFullYear());
if(dateVec[1])
{
theDate = dateVec[2];
document.write( ' (moved from ' + _days[theDate.getDay()] + ', ' + theDate.getDate() +OrdinalSuffix(theDate.getDate())+ ' '
+ _months[theDate.getMonth()] + ')');
}
return(dateVec[0]);
}
//
// Returns 'nd', 'rd', or 'th' for the ordinal of the given number as in:
// 1st, 2nd, 3rd, 4th.... 20th, 21st etc
//
function OrdinalSuffix(num)
{
var numMod = num%100; // Get it down to 0 - 99
if((3 < numMod) && (21 > numMod)) // ...but we say '11th', '12th' - not '11st', '12nd' !!
return('th');
numMod = numMod%10; // Get it down to 0 - 9
if(1 == numMod)
return('st');
if(2 == numMod)
return('nd');
if(3 == numMod)
return('rd');
return('th'); // Default
}
//
// Add 1 to the month [1 - 12] , if necessary add 1 to the year
//
function NextMonth(monthYearVec)
{
monthYearVec[0]++;
if(12 < monthYearVec[0])
{
monthYearVec[0] = 1;
monthYearVec[1]++;
}
return(monthYearVec);
}
//
// Return the last Xday (e.g. the last Friday) of the month
//
function LastXday(xDay, month, year)
{
daysInMonth = [31,28,31,30,31,30,31,31,30,31,30,31];
//
// Add one to February for leap years,
// Use the 400-year rule in case Cogers and Javascript still exist in 2100 AD...I think breaks in 5000 AD
//
// Shame to have make this fix here and not make it at the top with daysInMonth[] as a global array,
// but in general we don't know what year it is (although today.getFullYear() is a very good guess).
//
if( !(year%4) && (year%100 || !(year%400)) )
daysInMonth[1] = 29;
month--; // Reset month to range [0, 11] for Javascript functions.
//
// Get the *last* day of this month
//
var meetingDate = new Date(daysInMonth[month]+" "+ _months[month] +", "+year);
var dayOfWeek = meetingDate.getDay(); // 0 = Sunday , 1 = Monday , ...
//
// calculate the last xDay
//
if(dayOfWeek < xDay)
meetingDate.setDate(daysInMonth[month]-dayOfWeek-7+xDay);
else
meetingDate.setDate(daysInMonth[month]-dayOfWeek+xDay);
return(meetingDate);
}
//
// Return the date for the Nth Xday (e.g. the 4th Tuesday) of the given month and year
// 1 <= nth <= 4
// 0 (=Sunday) <= xDay <= 6 (=Saturday)
// 1 <= month <= 12
//
function NthXday(nth, xday, month, year)
{
var dom = 1; // Day of month
var meetingDate = new Date(dom+" "+_months[--month]+", "+year);
// Reset month to range [0, 11] for Javascript functions
//
// Calculate the nth xDay and reset the meetingDate
//
var daysTillXday = 1 + xday - meetingDate.getDay();
if(daysTillXday > 0)
{
dom = daysTillXday+(nth-1)*7;
} else
{
dom = daysTillXday+nth*7;
}
meetingDate.setDate(dom);
return(meetingDate);
}
//
// Return true if we would not have a Cogers meeting on this day due to public holidays or the holiday season
// Ref: Department of Trade and Industry Bank holidays FAQ: http://www.dti.gov.uk/er/bankhis.htm
//
function IsHoliday(theDate)
{
var dow = theDate.getDay(); // Day of week 0=Sunday, 1=Monday...
var dom = theDate.getDate(); // Day of the month
var month = theDate.getMonth()+1; // Set months from 1-12 to make it easier for me to understand
var year = theDate.getFullYear();
if(IsChristmas(dow, dom, month, year,theDate)) // Anything after 23rd December, sometimes even 23rd itself
return(true);
if(IsNewYear(dow, dom, month, year,theDate)) // Anything from 1st Jan until New Year's Day bank holiday
return(true);
if(IsEaster(dow, dom, month, year,theDate)) // The whole Easter weekend
return(true);
if(IsMayDay(dow, dom, month, year,theDate)) // First Monday in May
return(true);
if(IsSpringBank(dow, dom, month, year,theDate)) // Last Monday in May
return(true);
if(IsAugustBank(dow, dom, month, year,theDate)) // Last Friday in August
return(true);
if(IsSpecialBank(dow, dom, month, year,theDate))
return(true); // Special Bank holidays - e.g. Millenium Day, 60th Jubilee etc
return false; // Default - not a holiday
}
//
// Christmas
// No meetings between Christmas eve and end of December
//
function IsChristmas(dow, dom, month, year, theDate)
{
if((12 == month) && (dom > 23)) // There won't be any Cogers meetings on Christmas eve.
return(true);
//
// Policy regarding the 23rd December?
// No meeting unless its a Tuesday, Wednesday or Thirsday
// (not Fri, Sat or Sun, nor Mon)
//
if((23 == dom) && ((2 > dow) || (4 < dow)))
return(true);
return false;
}
//
// New Year holiday season
//
function IsNewYear(dow, dom, month, year, theDate)
{
if((month != 1) || (3 < dom)) // Ok if not close to the the beginning of January
return(false);
var nyd = new Date('1 January, '+ year);
var dow_nyd = nyd.getDay();
if((6== dow_nyd) || (0 == dow_nyd)) // If NYD falls on Saturday or Sunday then no meeting for dom=1,2,3
return(true);
return false;
}
//
// Return 'true' if theDate is between Good-Friday and Easter Monday inclusive.
// 1 <= month <= 12
// 0 = Sunday <= dow <= 6 = Saturday
//
function IsEaster(dow, dom, month, year, theDate)
{
//
// Assuming Easter Monday can never be later than 31st April, and Good Friday is never before 1st March
// So can't be Easter if theDate not in March or April
// Nor a holiday if day-of-week is Tuesday, Wednesday or Thursday.
//
if((month != 3) && (month != 4) || ((1 < dow) && (dow < 5)))
return(false);
//
// Algorithm found at: http://forums.wolfram.com/mathgroup/archive/2003/Apr/msg00336.html
// Uses Javascript Math library.
//
var a = year%19;
var b = Math.floor(year/100);
var c = year%100;
var d = Math.floor(b/4);
var e = b%4;
var g = Math.floor((8*b+13)/25);
var h = (19*a+b-d-g+15)%30;
var mu = Math.floor((a+11*h)/319);
var i = Math.floor(c/4);
var k = c%4;
var lambda = (2*e+2*i-k-h+mu+32)%7;
var easterMonth = Math.floor((h-mu+lambda+90)/25);
// March (3) or April (4)
var domSunday = (h-mu+lambda+easterMonth+19)%32;
// day of month of Easter Sunday
//
// Now check theDate is not between beginning of Good Friday and end of Easter Monday:
// calc number of days since beginning of March for theDate and EasterSunday, and then check difference
//
var eDays = domSunday + (4 == easterMonth ? 31 : 0);
var tDays = dom + (4 == month ? 31 : 0);
if((tDays < eDays -2) || (eDays + 1 < tDays))
return(false);
return(true);
}
//
// Is it the May Day bank holiday (first Monday in May)?
//
function IsMayDay(dow, dom, month, year, theDate)
{
if(month != 5) // May day bank holiday is in May...
return(false);
var mayDay = NthXday(1, 1, 5, year);
if(mayDay.getDate() == dom)
return(true);
return(false);
}
//
// Is it the August bank holiday (last Monday in August)?
//
function IsAugustBank(dow, dom, month, year, theDate)
{
if(month != 8) // August bank holiday is in August...
return(false);
var augustBank = LastXday(1, 8, year);
if(augustBank.getDate() == dom)
return(true);
return(false);
}
//
// Is it the Spring bank holiday (last Monday in May)?
//
function IsSpringBank(dow, dom, month, year, theDate)
{
//
// In 2002 the Spring Bank holiday was moved from Monday 27th May to Tuesday 4th June
//
if(2002 == year)
{
if((4 == dom) && (6 == month))
return(true);
else
return(false);
}
if(month != 5) // Otherwise, Spring bank holiday is in May...
return(false);
var springBank = LastXday(1, 5, year);
if(springBank.getDate() == dom)
return(true);
return(false);
}
//
// Is it a special bank holiday?
// Add in others as they occur - watch out if holidays have moved e.g. Spring Bank holiday 2002 was moved
//
function IsSpecialBank(dow, dom, month, year, theDate)
{
if((1999 == year) && (12 == month) && (31 == dom))
return(true); // Millenium holiday, Friday 31st December, 1999
if((2002 == year) && (6 == month) && (3 == dom))
return(true); // Queen's Golden Jubilee 2002 Monday 3rd June
if((2012 == year) && (6 == month) && (5 == dom))
return(true); // Queen's Diamond Jubilee 2012 Monday 5th June (Gawd bless 'er Maj)
return(false);
}