Doomsday rule: Difference between revisions

</pre>

=={{header|Wren}}==

{{libheader|Wren-date}}

We only use the above module to check the dates of the week given by Conway's method. The latter are worked out from scratch.

<lang ecmascript>import "/date" for Date

var days = ["Sunday", "Monday", "Tuesday", "Wednesday","Thursday", "Friday", "Saturday"]

var anchorDay = Fn.new { |y| (2 + 5 * (y%4) + 4 *(y%100) + 6 * (y%400)) % 7 }

var isLeapYear = Fn.new { |y| y%4 == 0 && (y%100 != 0 || y%400 == 0) }

var firstDaysCommon = [3, 7, 7, 4, 2, 6, 4, 1, 5, 3, 7, 5]

var firstDaysLeap = [4, 1, 7, 4, 2, 6, 4, 1, 5, 3, 7, 5]

var dates = [

"1800-01-06",

"1875-03-29",

"1915-12-07",

"1970-12-23",

"2043-05-14",

"2077-02-12",

"2101-04-02"

]

System.print("Days of week given by Doomsday rule:")

for (date in dates) {

var y = Num.fromString(date[0..3])

var m = Num.fromString(date[5..6]) - 1

var d = Num.fromString(date[8..9])

var a = anchorDay.call(y)

var w = d - (isLeapYear.call(y) ? firstDaysLeap[m] : firstDaysCommon[m])

if (w < 0) w = 7 + w

var dow = (a + w) % 7

System.print("%(date) -> %(days[dow])")

}

System.print("\nDays of week given by Date module:")

for (date in dates) {

var d = Date.parse(date, Date.isoDate)

System.print("%(date) -> %(d.weekDay)")

}</lang>

{{out}}

<pre>

Days of week given by Doomsday rule:

1800-01-06 -> Monday

1875-03-29 -> Monday

1915-12-07 -> Tuesday

1970-12-23 -> Wednesday

2043-05-14 -> Thursday

2077-02-12 -> Friday

2101-04-02 -> Saturday

Days of week given by Date module:

1800-01-06 -> Monday

1875-03-29 -> Monday

1915-12-07 -> Tuesday

1970-12-23 -> Wednesday

2043-05-14 -> Thursday

2077-02-12 -> Friday

2101-04-02 -> Saturday