javascript calender control

var A_TCALCONF = {
'cssprefix' : 'tcal',
'months' : ['January', 'February', 'March', 'April', 'May', 'June', 'July', 'August', 'September', 'October', 'November', 'December'],
'weekdays' : ['Su', 'Mo', 'Tu', 'We', 'Th', 'Fr', 'Sa'],
'longwdays' : ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'],
'yearscroll' : true, // show year scroller
'weekstart' : 0, // first day of week: 0-Su or 1-Mo
'prevyear' : 'Previous Year',
'nextyear' : 'Next Year',
'prevmonth' : 'Previous Month',
'nextmonth' : 'Next Month',
'format' : 'm/d/Y' // 'd-m-Y', Y-m-d', 'l, F jS Y'
};

var A_TCALTOKENS = [
// A full numeric representation of a year, 4 digits
{'t': 'Y', 'r': '19\\d{2}|20\\d{2}', 'p': function (d_date, n_value) { d_date.setFullYear(Number(n_value)); return d_date; }, 'g': function (d_date) { var n_year = d_date.getFullYear(); return n_year; }},
// Numeric representation of a month, with leading zeros
{'t': 'm', 'r': '0?[1-9]|1[0-2]', 'p': function (d_date, n_value) { d_date.setMonth(Number(n_value) - 1); return d_date; }, 'g': function (d_date) { var n_month = d_date.getMonth() + 1; return (n_month < 10 ? '0' : '') + n_month }},
// A full textual representation of a month, such as January or March
{'t': 'F', 'r': A_TCALCONF.months.join('|'), 'p': function (d_date, s_value) { for (var m = 0; m < 12; m++) if (A_TCALCONF.months[m] == s_value) { d_date.setMonth(m); return d_date; }}, 'g': function (d_date) { return A_TCALCONF.months[d_date.getMonth()]; }},
// Day of the month, 2 digits with leading zeros
{'t': 'd', 'r': '0?[1-9]|[12][0-9]|3[01]', 'p': function (d_date, n_value) { d_date.setDate(Number(n_value)); if (d_date.getDate() != n_value) d_date.setDate(0); return d_date }, 'g': function (d_date) { var n_date = d_date.getDate(); return (n_date < 10 ? '0' : '') + n_date; }},
// Day of the month without leading zeros
{'t': 'j', 'r': '0?[1-9]|[12][0-9]|3[01]', 'p': function (d_date, n_value) { d_date.setDate(Number(n_value)); if (d_date.getDate() != n_value) d_date.setDate(0); return d_date }, 'g': function (d_date) { var n_date = d_date.getDate(); return n_date; }},
// A full textual representation of the day of the week
{'t': 'l', 'r': A_TCALCONF.longwdays.join('|'), 'p': function (d_date, s_value) { return d_date }, 'g': function (d_date) { return A_TCALCONF.longwdays[d_date.getDay()]; }},
// English ordinal suffix for the day of the month, 2 characters
{'t': 'S', 'r': 'st|nd|rd|th', 'p': function (d_date, s_value) { return d_date }, 'g': function (d_date) { n_date = d_date.getDate(); if (n_date % 10 == 1 && n_date != 11) return 'st'; if (n_date % 10 == 2 && n_date != 12) return 'nd'; if (n_date % 10 == 3 && n_date != 13) return 'rd'; return 'th'; }}

];


function f_tcalGetHTML (d_date) {

var e_input = f_tcalGetInputs(true);
if (!e_input) return;

var s_pfx = A_TCALCONF.cssprefix,
s_format = A_TCALCONF.format;

// today from config or client date
var d_today = f_tcalParseDate(A_TCALCONF.today, A_TCALCONF.format);
if (!d_today)
d_today = f_tcalResetTime(new Date());

// selected date from input or config or today
var d_selected = f_tcalParseDate(e_input.value, s_format);
if (!d_selected)
d_selected = f_tcalParseDate(A_TCALCONF.selected, A_TCALCONF.format);
if (!d_selected)
d_selected = new Date(d_today);

// show calendar for passed or selected date
d_date = d_date ? f_tcalResetTime(d_date) : new Date(d_selected);

var d_firstDay = new Date(d_date);
d_firstDay.setDate(1);
d_firstDay.setDate(1 - (7 + d_firstDay.getDay() - A_TCALCONF.weekstart) % 7);

var a_class, s_html = '<table id="' + s_pfx + 'Controls"><tbody><tr>'
+ (A_TCALCONF.yearscroll ? '<td id="' + s_pfx + 'PrevYear" ' + f_tcalRelDate(d_date, -1, 'y') + ' title="' + A_TCALCONF.prevyear + '"></td>' : '')
+ '<td id="' + s_pfx + 'PrevMonth"' + f_tcalRelDate(d_date, -1) + ' title="' + A_TCALCONF.prevmonth + '"></td><th>'
+ A_TCALCONF.months[d_date.ge