> For the complete documentation index, see [llms.txt](https://trizen.gitbook.io/sidef-lang/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://trizen.gitbook.io/sidef-lang/programming_tasks/c/calendar_-_for_real_programmers.md).

# Calendar - for REAL programmers

```ruby
-> DT { ('DATE'.("\LWC") + 'TIME'.("\LWC")).("\LREQUIRE") }

-> MONTHS_PER_COL { 6 }
-> WEEK_DAY_NAMES { <MO TU WE TH FR SA SU> }
-> MONTH_NAMES    { <JAN FEB MAR APR MAY JUN JUL AUG SEP OCT NOV DEC> }

-> FMT_MONTH (YEAR, MONTH, STR="", WEEK_DAY=0) {
    STR  = "%11\LS\E%9\LS\E\12".("\LSPRINTF")(MONTH_NAMES()[MONTH-1],'')
    STR += (WEEK_DAY_NAMES().("\LJOIN")(' ') + "\12")

    -> DATE { DT().("\LNEW")("\LYEAR" => YEAR, "\LMONTH" => MONTH) }

    WEEK_DAY = DATE().("\LDAY_OF_WEEK")
    STR += (["  "] * WEEK_DAY-1 -> ("\LJOIN")(" "))

    -> LAST_DAY {
        DT().("\LLAST_DAY_OF_MONTH")(
            "\LYEAR" => YEAR, "\LMONTH" => MONTH
        ).("\LDAY")
    }

    (DATE().("\LDAY") .. LAST_DAY()).("\LEACH")({ |DAY|
        (WEEK_DAY ~~ (2..7)) && (STR += " ")

        (WEEK_DAY == 8) && (
            STR += "\12"
            WEEK_DAY = 1
        )
        STR += ("%2\LD" % DAY)
        ++WEEK_DAY
    })
    (WEEK_DAY < 8) && (STR += " ")
    STR += (["  "] * 8-WEEK_DAY -> ("\LJOIN")(" "))
    STR += "\12"
}

-> FMT_YEAR (YEAR, STR="", MONTH_STRS=[]) {
    MONTH_STRS = 12.("\LOF")({|I| FMT_MONTH(YEAR, I+1).("\LLINES") })

    STR += (' '*(MONTHS_PER_COL()*10 + 2) + YEAR + "\12")
    (0..11 -> ("\LBY")(MONTHS_PER_COL())).("\LEACH")({ |MONTH|
        MONTH_STRS[MONTH] && ->() {
            { |I|
                MONTH_STRS[MONTH + I] && (
                    STR += MONTH_STRS[MONTH + I].("\LSHIFT")
                    STR += ' '*2
                )
            } * MONTHS_PER_COL()

            STR += "\12"
            MONTH_STRS[MONTH] && __FUNC__()
        }()
        STR += "\12"
    })

    STR
}

FMT_YEAR(ARGV ? ARGV[0].("\LTO_I") : 1969).("\LPRINT")
```

#### Output:

```
                                                              1969
        JAN                   FEB                   MAR                   APR                   MAY                   JUN
MO TU WE TH FR SA SU  MO TU WE TH FR SA SU  MO TU WE TH FR SA SU  MO TU WE TH FR SA SU  MO TU WE TH FR SA SU  MO TU WE TH FR SA SU
       1  2  3  4  5                  1  2                  1  2      1  2  3  4  5  6            1  2  3  4                     1
 6  7  8  9 10 11 12   3  4  5  6  7  8  9   3  4  5  6  7  8  9   7  8  9 10 11 12 13   5  6  7  8  9 10 11   2  3  4  5  6  7  8
13 14 15 16 17 18 19  10 11 12 13 14 15 16  10 11 12 13 14 15 16  14 15 16 17 18 19 20  12 13 14 15 16 17 18   9 10 11 12 13 14 15
20 21 22 23 24 25 26  17 18 19 20 21 22 23  17 18 19 20 21 22 23  21 22 23 24 25 26 27  19 20 21 22 23 24 25  16 17 18 19 20 21 22
27 28 29 30 31        24 25 26 27 28        24 25 26 27 28 29 30  28 29 30              26 27 28 29 30 31     23 24 25 26 27 28 29

        JUL                   AUG                   SEP                   OCT                   NOV                   DEC
MO TU WE TH FR SA SU  MO TU WE TH FR SA SU  MO TU WE TH FR SA SU  MO TU WE TH FR SA SU  MO TU WE TH FR SA SU  MO TU WE TH FR SA SU
    1  2  3  4  5  6               1  2  3   1  2  3  4  5  6  7         1  2  3  4  5                  1  2   1  2  3  4  5  6  7
 7  8  9 10 11 12 13   4  5  6  7  8  9 10   8  9 10 11 12 13 14   6  7  8  9 10 11 12   3  4  5  6  7  8  9   8  9 10 11 12 13 14
14 15 16 17 18 19 20  11 12 13 14 15 16 17  15 16 17 18 19 20 21  13 14 15 16 17 18 19  10 11 12 13 14 15 16  15 16 17 18 19 20 21
21 22 23 24 25 26 27  18 19 20 21 22 23 24  22 23 24 25 26 27 28  20 21 22 23 24 25 26  17 18 19 20 21 22 23  22 23 24 25 26 27 28
28 29 30 31           25 26 27 28 29 30 31  29 30                 27 28 29 30 31        24 25 26 27 28 29 30  29 30 31
```