month_calendar.sf

#!/usr/bin/ruby

var mons = Hash(
                1  => 31,
                2  => 28,
                3  => 31,
                4  => 30,
                5  => 31,
                6  => 30,
                7  => 31,
                8  => 31,
                9  => 30,
                10 => 31,
                11 => 30,
                12 => 31,
           )

var t = Time.local

var day  = (t.day);
var mon  = (t.mon + 1);
var year = (t.year + 1900);

if (year % 400 == 0 || (year % 4 == 0 && (year % 100 != 0))) {
    mons{2} = 29
}

year--
var st = (1 + year*365 + year//4 - year//100 + year//400);
for i (1 ..^ mon) { st += mons{i} }

#
## Displaying the calendar
#

var monName = t.strftime("%B");

"%*s\n%s\n".printf(
                    (monName.len + 5) / 2 + 11,
                    "%s %d".sprintf(monName, year + 1),
                    "Su Mo Tu We Th Fr Sa",
                  );

' ' * 3 * (st % 7) -> print;

for i (1..mons{mon}) {
    printf(i == day ? "\e[7m%2d\e[0m " : "%2d ", i);
    st+i %% 7 && ((i != mons{mon}) && ("\n".print));
}

"\n".print;