Calendar

Calendar Calculation

Relations between calendar units

Year: 



Months:
 12 _{MONTH NAMES}


var additional_days = ( leap_year(y) ) ? 2 : 1;
Weeks:
 52 + ADDITIONAL DAYS

var calendar_weeks = 52; // Default
/**
 * To see different pure arithmetic solutions, refer to chapter `Day`
 */
var new_year = new Date(y, 0, 1);
var new_year_day_index = new_year.getDay(); // NEW YEAR DAY INDEX
if ( (NEW YEAR DAY INDEX == 3 && leap_year(y)) || NEW YEAR DAY INDEX == 4 )
    calendar_weeks = 53;
Calendar Weeks:
 CALENDAR WEEKS

var days = ( leap_year(y) ) ? 366 : 365;
DAYS:
 AMOUNT DAYS

Year: 		Month (zero based): 



var month_name = months[m];
Month name:
 MONTH NAME



var amount_days = last_date_of_month(y, m);
Days in MONTH NAME y:
 AMOUNT DAYS

/**
 * To see different pure arithmetic solutions, refer to chapter `Day`
 */
var tmp, i;
var first = new Date(y, m, 1);
var offset = (first.getDay() || 7) - 1; // OFFSET
var amount_days_month_before = last_date_of_month(y, (m - 1)); // AMOUNT DAYS MONTH BEFORE
var start = [];
var end = [];
var tmp2 = 1 - OFFSET;
while ( (tmp2 + 7) <= amount_days )
    tmp2 += 7;
var counter = 0;
for ( i = 0; i < 7; i++ ) {
    tmp = i - OFFSET + 1;
    if ( tmp > 0 )
        start.push(tmp);
    else
        start.push(AMOUNT DAYS MONTH BEFORE + tmp);
    tmp = i + TMP2;
    if ( tmp <= amount_days )
        end.push(tmp);
    else
        end.push(++counter);
}
First (partial) week:
 FIRST WEEK
Last (partial) week:
 LAST WEEK

Year: 		Month (zero based): 		Day: 



var month_name = months[m];
Month name:
 MONTH NAME


var date = new Date(y, m, d);
var day_index = date.getDay(); // DAY INDEX
var day_name = days[DAY INDEX];
Day name:
 DAY NAME


day_index = weekday(y, m, d); // DAY INDEX
day_name = days[DAY INDEX];
Day name:
 DAY NAME

/**
 * The hard and long way
 * (with useful side-effects)
 */




var reference_year = Math.floor(y / 400) * 400; // REFERENCE YEAR
var distance = date_distance(REFERENCE YEAR, 0, 1, y, m, d) - 1; // DISTANCE

day_index = (DISTANCE + DAY_INDEX_0_0_1) % 7; // DAY INDEX
day_name = days[DAY INDEX];
Day name:
 DAY NAME

var day_of_year = date_distance(y, 0, 1, y, m, d);
Day of year:
 DAY OF YEAR

var new_year_distance = date_distance(reference_year, 0, 1, y, 0, 1) - 1; // NEW YEAR DISTANCE
// Sunday must be `7`, not `0`!
var new_year_index = ((NEW YEAR DISTANCE + DAY_INDEX_0_0_1) % 7) || 7; // NEW YEAR INDEX
var calendar_week = (NEW YEAR INDEX < 5) ? Math.ceil(day_of_year / 7) : Math.floor(day_of_year / 7);
Calendar week:
 CALENDAR WEEK